different behaviour on identical PLCS

[AlessandroLeidi]

I am using this library to communicate with 2 PLCs, both of them are s7 1200, to be precise 6ES7 214-1AF40-0XB0 with V 4.5.1 firmware on Tia Portal 17. One of them is working properly , the other signals connected but on the debug reports "Error: PLC error [0x8104]: This service is not implemented on the module or a frame error was reported". I checked the HW configurations for differences, checked the cabling, but they are connected directly, and the ping and the test on the port work properly, I tried to create a third node always pointing to the second PLC, but to no avail. What could be the issue? I checked on the configuration and the Allow Get Put is ON on the configuration, so it's not the most obvious cause