If the light on the dash is lighting up and the PTO is not engaging, then it could be an air gap or shorted winding issue (or both.) How much did the air gap need to be adjusted?
If the light does not even get driven when the PTO switch is turned to ON, then it might be a fuse/holder fault, or a safety interlock issue. Here is the wiring in that area, and the fuse locations:
Note that the 10 AMP fuse F2 (callout A in the illustration...) is the one that allows the TDCM to properly sense the state of the seat switch. Verify that it is not blown. If power gets that far, you may have a loose connection in the wiring harness going back to the seat switch or a faulty switch itself.
If the dash lamp does light up when the PTO switch is ON, but you don't get engagement, there is likely a fault in the PTO winding itself -- sometimes these will open up at elevated temperatures. After the tractor cools, does the PTO engage? You can measure the resistance of the PTO winding to see if it is partially internally shunted...it should be in the range of 3.4 to 4.9 ohms or so, but could be considerably less if several internal shorts exist.
Let us know what you find...