here are the steps I take when having a problem with connection between the SYSTECH and the NCRs:
(and I know I have a good internet connection to the device)

exit PPMSrvr
remove power from systech
exit RPRO (put invoice on hold?)

(at this point you may want to reboot also – about 10% of time it helps)

power to systech (now this has been off about 5 seconds)
restart RPRO
new receipt (held?)
tender cc