Hi Patrick
Check all your telegram is getting created and and you are getting conformation back to sap.
and use queue type resource with MFS.
check all structures used
Material Flow System (MFS) Telegram Processing Define Telegram Structure -> Define Telegram Structure for PLC
And
Material Flow System (MFS) Telegram Processing Define Telegram Structure -> Define Telegram Structure for PLC Interface Type
check all structure is working as expected.
Regards
Suraj