Cannot make a rack and pinion

@daniel_ramirez154 , I was not able to figure out the specific cause of your problem.  But when struggling with a model it can be helpful to isolate the specific components involved and focus on the individual tool.  The full assembly offers too many opportunities for conflicting mates and other complications.

I stripped your model down to the bare essentials to explore the rack & pinion relation.  Focus on the three key components:

1. Base (a convenient frame of reference to mate the other components to)
2. Pinion
3. Rack

Note that I added a mate connector to the rack in the Part Studio, with the Z-axis oriented along the center-line (for the slider mate).  I added a similar mate connector to the base plate in it's Part Studio (also oriented in the direction that the slider mate will move).

Insert those three components into a new assembly:

1. FIX the Base Plate (to lock it in place)
2. Apply REVOLUTE mate from Base Plate to Pinion
3. Apply SLIDER mate from Base Plate to Rack (using the custom mate connectors created in the part studios)
4. Apply RACK & PINION relation between the REVOLUTE and SLIDER

Back in the Part Studio I edited the Z-offset on the RACK mate connector to get at least crude visual alignment between mating teeth in the assembly.  In the gear relation I entered 0.55*PI inches for the DISTANCE PER REVOLUTION (because 0.55in appears to be a reasonable approximation of the "pitch diameter" of your pinion).

Here is a link to the simplified model:  https://cad.onshape.com/documents/f0f2f7e73cad905425f30d23/w/fb1a805815d39c4d614cbcae/e/6a6af9d42fa03e0e611cb31a

I hope that helps.