Lifestride 9100HR Power to Buttons but Belt does not start.

Not sure you can get 12 db from 6 elts.
From link below, looks like you'll need 8 or so.
https://www.electronics-notes.com/articles/antennas-propagation/yagi-uda-antenna-aerial/gain-directivity.php
Here's a design of one with 6 elts. You can size the elts proportionally to your desired freq. But it has less gain that you are looking for.
https://273k.net/gsm/designing-and-building-a-gsm-antenna/yagi/
If you want really high forward gain, maybe try a corner reflector, which will give you the desired db.
http://www.microwavetools.com/corner_reflector/
You could also try a rhombic, which can have extremely high gain if you have the space for it. There are many articles on rhombic design available.

If you wish to get some details About treadmill Error codes ; check the site linked here. Pull up older posts almost all treadmills are listed . Surf the site with patience.
http://electro-medical.blogspot.com/

press 125 enter or 5125 enter display will read "fill waxer full"

see this steps and fix it. .Of course you must read your instr. manual or download from www. iconservice.com
When the treadmill is not in use, press the "Stop," "ENTER" and "QUICK START" buttons in rapid succession. The "RESET" button can also be used, in place of the "Stop" button.

2 Press the "ENTER" button three times to access the treadmill's error log.

3 Press the up or down arrows to scroll through the error codes, if necessary for club or personal logging purposes.

4 To view the treadmill's odometer reading when a particular error code was elicited, press "SELECT" while a particular error code is displayed.

5 To clear the error log, press "QUICKSTART" for a minimum of four seconds while viewing the list. Prompts will appear on the display and let you know when the log has been deleted.

proceed with the instruction manual maintenance, if you do not have go for free download : www. fitness.manualsonline.com or www.iconservice.com

RUN THE software calibration for diagnose, troubleshooting, and fix it.

sincerely. God bless you

Typically a non start up of any electrical Exercise equipment raises alot of red flags If this treadmill will not start Check the internal fuse MAKE SURE ITS NOT PLUGGED IN!!!! UNPLUG IT FROM THE WALL
2 If there is NO Fuse and you just bought it new Return it for an exchange.
3 Check your wall outlet for less then 5 Bucks you can buy a wall outlet tester that tells you if your Outlet is good Or Bad.4 DO NOT Attempt to service this item on your own the way they make treadmills you have to have a qualified service tech come out and fix it because the risk of serious shock or death is emminent.

Have you checked the drive belt @ the motor, if it is OK then check the fuse, if it is ok then the brushes in the motor may be worn out

Manuals for the Jack LaLanne Power Juicers can be found here:

http://www.powerjuicer.com/power-juicer-manuals.php

You might take time to browse the site, you will find How To videos, Tips and recipes.

apparently you've got the wrong size belt.... no other explanation.

iv had similar problems, only happened once tho - i switched it on after a few mins it would go off.

iv read to dismantle the stop switch, clean and replace the microswitch. where can the microswitch be found from?

also, is the red stop switch that needs looking at? how can i remove it?

i was wondering on how i can service/maintain this properly, can anyone advise my on how to give this a service.