The OTK solution Kit injects a server module file, but this module file doesn't get loaded for unknown reason.
"OTK Resource Issuing", is not there, and thus OTK was not able to issue token.
Release : 10.0
Some old version of Mime tactical assertion was still present on this gateway (old 9.3/9.4 instead of new 10.0).
Once that old version of the assertion was removed and only the 10.0 version of the assertion was kept , it was working fine.