Beckhoff

Hey Guys,some of you know so much about this Topic so I hope I can find someone in the mood to help me.Im trying to make a CNC 3-Axis on Raspberry PI5 and Beckhoff, the problem is that im completly new in this topic and try to learn as much as possible but i got already stuck in the beginning. EtherCAT works fine and i got the "Koppler" and Cards but if im trying to get them into LinuxCNC like some videos teach the Programm wont start anymore

If i start i get the message: Failed to register PDO entry: No such file or directory
LCEC: master 0 PDO enty registration failed


Thanks for everybody who can help me with this and invests some of his time for me