You can tell if your EEPROM is turned on by looking at your Configuration.h file. It will have a couple of lines towards the bottom:

//#define EEPROM_SETTINGS
//to disable EEPROM Serial responses and decrease program space by ~1700 byte: comment this out:
// please keep turned on if you can.
//#define EEPROM_CHITCHAT

If you see the // they are commented out and the EEPROM is turned off.

M503 may not tell you about the Z_PROBE_OFFSET. There is a bug depending upon which version of Marlin you are using. Who ever did the early Auto Bed Leveling didn't realize you could print EEPROM values with M503. That has been fixed in later versions but if you don't see a number, it is probably because you have the wrong version of Marlin.

I would do a M502 and M500 either way. Get everything sync'ed up to what the Configuration.h file has for values.