Hi Tom,
Any entries in SM58?
Since the ECC system is upgraded, service user roles and authorizations might be changed. please check it..
Check the RFC destinations " XI_IDOC_DEFAULT_DESTINATION " in NWA and RFC destination which you created in ECC.
In your idoc communication channel make the RFC parameters to manual.
Please go through the below steps once again and ensure everything is correct.
IDOC_AAE To File with all Configurations
Regards
Bhargava krishna