Why can't the s600 evaluate the EnDat encoder after replacing the motor?

In all likelihood the application was installed in 2004. The old motor had a built-in EnDat encoder with small memory range. Heidenhain changed the memory range of EnDat encoders in 2005 (see FAQ Feedback).

EnDat encoders with expanded memory range can be evaluated with all S300/S700 drives and with S400/S600 drives from firmware version 4.94.

For applications with firmware version lower than 4.94, the firmware version 3.67 must be loaded, which has been produced for this purpose ([[File Selector]]).