How do I get wi-fi connection. I have inputted information for the wi-fi it says saved, then when you go to connect it says authentication problem and cannot complete registration.

• Plug your Echo Dot into a power outlet.
• Open the Alexa app.

Saving Your Wi-Fi Passwords to Amazon FAQs.

Optional - Connect to a public network: Enter any required information if you are connecting to a public network that requires a web browser to sign in, like a school or hotel. The information could be a pre-shared password, room number, or just a button to accept conditions for using the network. This information cannot be saved to Amazon. Contact the network owner for more information.

Select Connect. After your device connects to your Wi-Fi network, a confirmation message appears in the app. You're now ready to use Alexa.

The Kindle Paperwhite automatically scans for Wi-Fi networks that are in range of your device. If one networks are found, the device will connect automatically. If a password is required, a screen appears asking you to input that information. Generally, the process is quick and easy.
Occasionally, however, you may need to connect to the Wi-Fi network manually. Follow these steps:

1. Tap Menu?Settings.
2. If the network to which you want to connect appears in the list, tap that network.You're finished!
3. If the network to which you want to connect doesn't appear in the list:
   
   1. Tap Other.A dialog box named Enter Wi-Fi Network appears, along with the on-screen keyboard.
   2. Using the onscreen keyboard, enter the network name and, if applicable, the password.
   3. Tap the Advanced button.
   4. Work through the series of screens, entering information related to the network, including connection type, IP address, and security type.
      Advance through the screens by using the up and down arrows.
      If necessary, contact the person who set up the network for assistance with filling in this information.
   5. When all the necessary information has been entered, tap the Connect button to join the network.

If your Kindle Paperwhite is connected to your home network but can't connect to Amazon, you may need to reestablish the connection. Tap Menu?Settings?Wi-Fi Networks, and then tap the network that has a check mark to its left. When the Forget Network? dialog box appears, tap Forget. You'll have to reselect the network and enter the password (if one is required).
If you're having trouble connecting to your home network, unplug the Wi-Fi router, wait at least 60 seconds, and then plug it in and wait for the network to restart.
If this does not work....follow this link and do a factory reset.
http://www.wikihow.com/Reset-a-Kindle
Good luck.
Semper Fi,
DrZ

If you want to resolve the issue of wifi in kindle then follow given the link:
How To Resolve The Issue Related To Wi-Fi Connection Through Amazon Kindle...

You can also take kindle help by making a call on kindle customer service number @ +1(844)-305-0086 (Toll-Free)

It will say Authenticating problem unless you have the passkey to the other WiFi networks. So unless its your WiFi or an open network you won't be able to connect.But you can try rebooting your device.

Try it with a different router. Use a friends. Your router may have to be adjusted.
Go on the manufacturers web site and see if your problem is listed.

You can try this and see if it works for you:

Connect to Wi-Fi networks Some of this information applies only to devices running Android 5.0 and higher. If your device is running 4.4 or lower, the Menu icon looks like this . If your device is running 4.3 or lower, the Settings icon looks like this .
You can connect to Wi-Fi networks with your device, as well as add networks you use often or remove networks you don't use any longer. You can also change the settings for saved Wi-Fi networks on your device.
Keep in mind that your device will remember networks you connect to, along with security details, and connect automatically when in range.

Turn on Wi-Fi and connect to a network

1. Open your device's Settings menu .
2. Under "Wireless & networks," touch Wi-Fi.
3. Touch the Wi-Fi switch to turn it to the On position.
4. You'll see a list of saved and available networks.
   • Secured networks display a lock icon and ask for a password to connect.
   • Your device will remember networks it connects to and automatically connect to them when in range.
   • You can forget a saved Wi-Fi network if you don't want your device to connect to it automatically.
5. Touch a network name from the list of available networks to connect to it.
   • Android 5.0 or higher: If the saved network you want to connect to isn't showing up in the list of networks on your screen, touch the Menu icon in the top right corner of the screen. Touch Refresh to reload the list of networks. Touch Add network and enter the network's name (SSID) and other security details, if needed. Then touch Save.
6. Once connected, your device will say "Connected" under the network name.

Once you've connected to a network, it will show up in your Saved networks list. If you have trouble connecting to Wi-Fi, try the following steps:

Solution 1.Check wireless connection.
The first step of diagnosis have to any other device connected to the same network, ensure the wireless connection is working fine, or verify the settings of your wireless router to correct it.
2.Check your Keep Wi-Fi on during sleep Settings.
Owing to Wi-Fi sleep policy your Wi-Fi connection may be going to get disconnected every now and then.
Tweak this policy to keep your Wi-Fi connection awake.
[Settings] >>[Wi-Fi]>>[Advanced]>> Check [Always] to keep the Wi-Fi on during sleep.
Save changes and exit all the screens. Your Wi-Fi will never get disconnected again due to this policy.

3.Check signal strength of wireless connection.
The performance of a wireless network connection depends in part on signal strength.
You have to connect the Wireless network where the signal strength is strong.
Check Wireless network signal strength icons in notification bar.

4.Try to turn off/on Wi-Fi on the device.
First to turn off Wi-Fi, [Settings]>>[Wi-Fi] >>[turn Wi-Fi to off].
And then to turn on Wi-Fi, [Settings]>>[Wi-Fi]>>[turn Wi-Fi to on].

5.Try to forget network on the device.
Forgetting wireless networks allow your tablet/phone to reset some settings.
[Settings]>>[Wi-Fi]>>Press & hold your[Net Work Name(SSID)]for 2 seconds.
>>Select[Forget Network]>>Re-Connect your wireless networks if it's disconnected.

6.Try to reboot your device.
7.Make sure your firmware is up-to-date.
>>Select[Settings]>>[About tablet]>>[System Firmware Update]>>[Check Update].

8.Try to reset your device.
Note: once RESET was performed, all data, apps, settings and personal information will be deleted after initialization.
Third-party programs might be the major probability of Tablet/Phone instable, suggested to have a full reset for the device if the situation persists.
[Settings]>>[Backup&reset]>>[Factory data reset]

9.Try to other wireless connections.
If steps above were not able to solve internet connection problem still, please try other wireless connections if available, otherwise contact your networking provider to technical support.

I assume you're using a secure Wifi connection with a password and it seems like that authentication is not working. You could try using an open wifi access point to eliminate the possibility of this authentication issue.

Authentication often means "password protection" for the specific wifi connection. Usually your software will present a "dialogue" box telling you a password is necessary and give you an opportunity to enter one.