No suitable sender agreement found on single stack system

Dear experts,

I am currently doing some tests on a PO 7.31 system.

I have created a simple file to file scenario where I just want to route a file from point to point without creating any content on the design part.

So I created an integration flow with two dummy service interfaces. For sender and receiver I am using a BC, one sender and one receiver FTP file channels have been created. All objects have been activated and are showing up as consistens when I am doing a cache check from NWDS.

Now in the CC monitor for the file sender channel I am getting the message "No suitable sender agreement found".

I am not sure if I am missing any step in the iFlow, but I have checked all the tabs and cannot seem to find a missing setting. Also I have start/stopped the CCs and did some dummy changes / reactivations of my objects. Unfortunately none of this helped.

Do you have any idea what else could be the reason for this error?