Transmission does not shift into gear?

How does the clutch pedal feel does it seem normal or mushy? I would start by checking the clutch fluid level and if down check the master and secondary cylinder for leaks.

Here is a guide and video to help:

https://youtu.be/EpBMj5ZY_bo

and

https://www.2carpros.com/articles/clutch-doesnt-work-sometimes-or-not-at-all

Here is how to change out the master in case you need it. Check out the images (below). Let us know what happens and please upload pictures or videos of the problem so we can see what's going on.