Balance Board (Wii) won't power on - Nintendo Wii Fit - Balance Board + Game Console

It's either not establishing a connection with the Wii, or it's batteries need changing. I personally have never had to connect a balance board with the Wii for the first time, I only played with it at my friend's house.

Important Note!
Do Not use "One-Time Mode" sync.
Syncing can be completed only if a compatible game disc is running in the console.The Wii Balance Board may need to be synced to each compatible game individually.Some games may require you to go into a specific screen to sync the Wii Balance Board.These sync settings will be saved even after the console is turned off.
1. Insert a Wii Balance Board compatible game disc in the Wii console.2. Use the Wii Remote to select the Disc Channel from the Wii Menu, then select "Start" to begin the game.3. Open the SD Card slot cover on the front of the Wii console.4. Remove the Battery Cover on the bottom of the Wii Balance Board.
5. Press and release the SYNC button on the Wii Balance Board. The Power LED on the board will start blinking.
6. Press and release the SYNC button on the console while the Power LED on the board is still blinking.7. The Power LED will stop blinking and light steadily once the synchronization is complete.8. Replace the battery cover and return the board to the normal operating position.

If you haven't already tried to replace the batteries, do this (if you have, this is useful information to include in your problem description :D). If that hasn't worked, you may need to re-sync the board with your Wii.
1. Power on your Wii console (there is no need to power on your balance board at this time).
2. Open the SD card slot cover on the front face of your Wii to reveal the red Sync button on the Wii.
3. On the bottom of your balance board, remove the battery cover to reveal the red Sync button on the balance board.
4. Press the Sync button on the balance board (there is no need to keep it depressed; simply press and release). You will notice the power LED on the power button on the balance board blinking.
5. Now press (and release) the Sync button on the Wii console. After the LED stops blinking, the Sync is complete.
If this does not fix your balance board, it may need to be repaired or replaced. Contact Nintendo and provide warranty information if applicable.
Good luck!

Synching can be completed only if a compatible game disc is running in the console. Compatible game discs (such as Wii Fit) will display the Wii Balance Board icon on their packaging.
The Wii Balance Board must be synced to each compatible game individually.
These sync settings will be saved even after the console is turned off.

Follow these directions to sync the Wii Balance Board (so that it is recognized by the Wii console):

Insert a Wii Balance Board compatible game disc (such as Wii Fit) in the Wii console.


Use the Wii Remote to select the Disc Channel from the Wii Menu, then select "Start" to begin the game.

Open the SD Card slot cover on the front of the Wii console.

Remove the Battery Cover on the bottom of the Wii Balance Board.

Press and release the SYNC button on the Wii Balance Board. The Power LED on the board will start blinking.

Press and release the SYNC button on the console while the Power LED on the board is still blinking.

The Power LED will stop blinking and light steadily once the synchronization is complete.

Put four AA batteries into the battery housing located on the underside of the Wii Balance Board.

Insert a Wii Balance Board compatible game into the Wii system.

Select the "Disc Channel" on the screen with the Wii remote, and choose "Start."

Open the SD card slot to reveal a sync button on the Wii system. This is located behind a cover under the power and eject buttons.

Turn the Wii Balance Board upside down.

Remove the battery cover under the balance board to reveal another sync button.

Pres the sync button on the balance board, then press the sync button on the Wii. Do not hold down the buttons. You know it is synchronized when the blue light on the Wii Balance Board stays steady

Place the board on a flat surface directly in front of the TV. Face the power button away from the TV.

First thing to do is install fresh batteries.If the Wii Balance Board is still experiencing power problems after trying new batteries and ensuring that they are inserted correctly, please call 1-800-255-3700 for assistance


http://www.nintendo.com/consumer/systems/wii/en_na/ts/balanceBoard.jsp

All i had to do was SYNCHRO the board by pressing the synchro button on the wii balance board were the battries go, the power LED will blink (note once the power LED has started blinking, stop pressing the synchro button)
THen you need to press the synchro button on the wii console, while the wii balance board's power LED is blinking

If the Wii Balance Board fails to operate, or operates incorrectly, follow the steps below before seeking
assistance.
A. Check the batteries.
B. Check to be sure there is nothing pressing against the bottom.
C. If you are using it on soft carpet, put the foot extensions on.
1. The Wii Balance Board does not respond.
• Make sure the power is turned on. The blue Power LED should be lit if the Power Button has been
pressed. (The Power Button faces away from the TV.)
• Make sure the board has been placed correctly (see page 6).
• Make sure the batteries have been inserted correctly and are not been depleted.
• Make sure the game you are playing is compatible with the Wii Balance Board.
• Review the synchronization procedure on pages 7-8 and make sure this has been done correctly.
This procedure must be done for each Wii Balance Board compatible game.
• If, after verifying the steps above, the Wii Balance Board does not work, try the following:
1. Turn off the power of the Wii console with the POWER Button on the front of the console.
2. Unplug the power cord from the wall outlet for a few seconds, then plug it back in again.
3. Turn on the power of the Wii console.
4. Repeat the steps in this Operations Manual for setting up the board.
If the Wii Balance Board still does not work, follow the information at the bottom of this page.
2. Control of the Wii Balance Board is inconsistent or seems incorrect.
• Review the Instruction booklet for the game you are playing to make sure you are performing the
correct actions for that game.
• Make sure the board has been placed correctly (see page 6).
• Try using the Wii Balance Board foot extensions if you are using the board on carpet (see page 10).
• Make sure there are no people or other objects between you and the Sensor Bar.
• Avoid interference from other devices. If communication seems to be affected by other devices
(wireless LAN, microwave ovens, cordless devices, computers) move to another location if possible,
or turn off the interfering device.
If the Wii Balance Board still does not work, follow the information below.
If the Wii Balance Board still does not work, an operational check procedure is available
in the Options Menu of the game you are playing. See the Instruction booklet included
with the Game Disc for more information. If your Wii Balance Board does not operate
correctly after all of the above steps, visit support.nintendo.com for assistance and
additional troubleshooting and repair options or call 1-800-255-3700.

If there is no reason for the Wii Balance Board to be on, it will automatically turn off. Start up a game that uses the Balance (Wii Fit) and it will tell you when to turn on the Wii Balance Board. If you still have problems, try to sync the Balance Board again.

are you able to get any of your controllers to connect? if not it could be a issue with your sensor bar. please provide a bit more info

but try this first

Synchronizing the Wii Balance Board with your Wii Console
IMPORTANT: To operate correctly, the Wii Balance Board must be synchronized with the Wii console using Standard Mode Synchronization. Follow the steps below to synchronize the board to the console.

• This procedure must be followed for each Wii Balance Board compatible Game Disc.
• These synchronization settings will be saved even if the console is turned off.
• This procedure can be completed only if a compatible Game Disc is running in the console.

1. Press the EJECT Button on the front of the Wii console and remove any
   game disc if necessary. Insert a Wii Balance Board compatible Game Disc.
2. Use the Wii Remote to select the Disc Channel on the Wii Menu screen and select START.
3. Open the SD Card slot cover on the front of the Wii console.
   NOTE: Close the SD Card slot cover when you are finished with the synchronization procedure.
4. Remove the Battery Cover on the bottom of the Wii Balance Board.
   NOTE: Replace the Battery Cover when you are finished with the aynchronization procedure.
5. Press the SYNCHRO Button (SYNC.) on the Wii Balance Board. The Power LED on the board will start blinking (for up to about 20 seconds).

Press the SYNCHRO Button (SYNC.) on the console while the Power LED on the board is blinking.

1. IMPORTANT: Do not press and hold the SYNCHRO Button on the Wii console down for more than 10 seconds. This will delete all of the Standard Mode synchronization information for all Wii Remotes that you use with that console.
2. The Power LED will stop blinking and light steadily once the synchronization is
   complete. You are now ready to play the Wii Balance Board compatible Game Disc. Please refer to the instruction booklet for the Game Disc you are using for further information on gameplay.

• Only one Wii Balance Board can be synchronized to a Wii console at a time. Up to a total of 10 Wii Remotes and accessories can be synchronized to a console at any time with the Standard Mode procedure. If additional synchronizations are made, the oldest existing ones will be overwritten.
• The Wii Balance Board can only be synchronized to one console at a time using the Standard Mode procedure. If you change the console you are using the board with, you will have to repeat the synchronization procedure each time.
• The Wii Balance Board uses the Player 4 (P4) connection. If a Wii Remote is actively using P4, that remote will be disconnected while the board is being used.