Idoc adapter - No service for a system in Integration directory

Hi,

I'm trying to send a custom IDOC from an R3 system to an XI instance.

All settings that I can see using transactions IDX1 IDX2 and IDX5 seems to be correct, but the IDOC doesn't reach the IS.

SM58 in the sender system reports the error:

"No service for system SAPXXX, client nnn in Integration Directory".

Do I have to create the service? How?

Thanks for any suggestion.

Simona