Craig,
If your PIA-S display is not working with Mach4, does it work with Mach3?
Revert the Firmware back to Mach3 and if and only if Mach3 cannot also display correctly then following the instuctions below.
I had an issue that mine stopped displaying correctly my cable must have came slightly loose.
VistaCNC support instructed my on how to fix it by removing the cable and provided the following instructions.
One thing you can do is to check if the ribbon flat cable connecting the LCD module to the main board is loosen.
Remove the back 6 screws and gently open the back, take care as it has wires attached.
I attached a picture and a youtube move that show how to remove and insert the flat cable. Insert the LCD module side first. On both LCD and board end, the tin side of the cable is face down.
https://www.youtube.com/watch?v=C9PwK9eGrCYThat was my issue, I hope it is yours as well.
Regards,
Mauri.