The incline and decline not working

Spring of the seat may be damaged

You've to check the incline and decline limit switches also the incline motor
If you wish to get some details about treadmill repair and service ; check the site linked here. Pull up older posts.
http://electro-medical.blogspot.com/

This is conjecture but the incline motor is likely attached to a worm gear that lifts and then lowers the incline. There is also likely some kind of automatic "clutch" that disengages the motor from the worm drive after the raise or lower sequence is complete. If this clutch is broken or malfunctioning, then it may be trying to "grab" the worm gear when it is not supposed to (when not raising or lowering) or conversely, it may be losing its grip on the worm gear when the incline is happening. The clutch is likely controlled by an electric solenoid which may be malfunctioning. All this to say that it may be time to call a repair person.

Bad contact in the switch

Sounds like the button on the panel is stuck somehow, I think this because when you switch the wires this would reverse the polarity to the incline motor.

can you tell if the panel is recognizing the pushing of the incline buttons, like with a beep or light or something? If it didn't seem like it's responding this may be because one button is constantly stuck down.

RUN the software calibration for easy diagnostic and fix it.
Go to the HOOD cover motor, and follow the steps , or use the owner manual for follow the steps.
God bless you

please RUN the software calibration for easy diagnose, troubleshooting and fix it.

God bless you

This sounds like the treadmill is running an incline calibration. It will run to fully inclined, then to minimum incline.
It should not do this every time you want to operate the machine, but they will do it automatically if the operation of the machine is stopped by the power being interrupted..

My wife had the same problem with her treadmill. I turned the beast on it's side, and unscrewed the plastic casing that houses the motor, computer, and all the electronics to the treadmill. I unplugged the incline/decline motor. Then on the bottom of the treadmill the long threaded rod that causes the incline needed to be moved. So I unbolted it from the catch, and manually screwed the rod back in with a wrench. Now the treadmill works fantastically, of course the incline/decline mechanism has been disabled, but I would rather have a treadmill with the incline disabled than have one always on 100% incline. Hope you found this helpful :)

i just called the manufacturer on this and found out i have a faulty control panel, but these are the steps they told me to go through to reset. If it works, then you are good, if not, you may also have a control panel issue.
1. plug in and turn on treadmill, keep red key out
2. press and hold the stop button and speed up button at the same time and hold them while you insert the red key
3. after red key is inserted, let go of both buttons
**CAUTION - be sure to stand on side bars of treadmill, clear of the belt for this next part bc it will go VERY FAST***
4. press stop button once
5. press speed up button until it reads 85 (see what i mean?!)
6. press stop button once
7. press incline down or up one time and it should get back into normal mode. mine just started a series of flashing lights and "8"s in all the "windows" so my panel needs to be replaced. here is the number i called - 1-877-993-7999. Good Luck!