Cause

You use the PLC import interface Beckhoff TwinCat: No bus port (output) was found for a bus port (input) at the device <x> named in the message during importing. The matching bus port (output) is always searched for at the predecessor address <y>.

Solution

Check whether a bus port (output) exists for the bus port (input) of the device <x> named in the message at the predecessor address <y>.