It might be as simple as cleaning the contact in the switch, or it may be worn and need replacement.
I have had a couple of starters that either would not turn or would do so intermittently, cleaning the contact and replacing button switch on top of starter fixed the problem. The starter contact sometimes developes a groove in the surface so a new
Switch sometimes will cure that. The contact also may develop some corrosion from time and arcing. Another item would be if cab rot has let the cab shift to where stomping the starter and bending floorboard is the only way you can get full contact between button and starter contact.
With my 38 I often just reach in with my hand and push starter pedal that way I can use my thumb on gas pedal at same time. It doesn't have to be pushed real hard. No seats is the reason for not just climbing in and using conventional foot method.
