It fills with water but won't go into the wash or spin cycle. I did the diagnostic test and got an F-25 error code. What does this mean?

The F25 error means:

DRIVE MOTOR TACHOMETER ERROR. If the control is unable to properly detect motor speed, the machine shuts down.

The tachometer is built into the motor on these models so if the error persists you will need to replace the motor. 

The motor you need for your model is linked below:

https://prismparts.com/products/whirlpool-washer-drive-motor-pp4765106

The video linked below shows how to replace the motor on those model washers. The model in the video may not be your exact model but it's about the same replacement procedure.

https://www.youtube.com/watch?v=xjJX_QkgsFI