I just dug out my p2s to see if it would work at all with the p4s binary - I also got the "LinuxCNC" display and nothing worked. I swapped to the p2s binary and replaced all occurrences of p4s in vc-p4s-pp.hal to p2s and my pendant started working. Maybe there's an issue with the p4s binary? You could try installing the p2s binary - perhaps it would come out of the "LinuxCNC" stage - even if other functions might not work. I don't know how compatible the pendants are, but this might be a way to find out if the binary is at fault.
Using the p2s binary and the modified hal file I've managed to get the jogging, axis zero (for X, Y and Z), estop and machine on/off working. I thought the feed and speed overrides would also work without PathPilot mods but I was apparently mistaken. It appears that the p4s has individual buttons to goto 0 on X, Y and Z. The p2s doesn't have these but they should be easy to get working - if we can get the pendant to work at all!
By the way, the pendant seems to have an issue when the units are changed to metric in PathPilot.
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