I've had the same issue as you a couple of times, but it was 100% my fault & was easily fixed.
My problems came from buying second hand vintage lenses & in my keenness to try them out, not checking for dirt on the lens, which got into
the body of the camera through the autofocus screw and stopped it working.
Previous posters have mentioned contact cleaner, but to be more precise, the thing you need is electronic cleaning solvent - isopropyl alcohol
Isopropyl Alcohol 400ml | Maplin. Carefully spray a little into the autofocus screw & the MF/AF switch, then wait until the smell of the alcohol has completely gone.
This means the alcohol will have completely evaporated, taking the dirt with it.
After this, the autofocus should be back to normal.
If it still doesn't work and you decide to desert Pentax, I'd buy Nikon rather than Canon!