uCMDB to Service Now Enhanced adapter not starting

Dear community, 

While trying to set-up a new Integration between our uCMDB 2019.05 CP27 and Service Now, using the OOTB Service Now Enhanced adapter, we notice that this Integration is not starting properly, giving following errors : 

From the probe-error.log

<2021-05-20 11:28:40,954> [ERROR] [AdHoc:AD_HOC_TASK_PATTERN_ID-22-1621502920702] (AbstractDataAccessContainerManagerImpl.java:228) - Failed to start adapter [SNOW].
com.hp.ucmdb.federationspi.exception.DataAccessGeneralException

And the last entry in the server error.log is 

2021-05-20 11:28:40,939 INFO [AdHoc:AD_HOC_TASK_PATTERN_ID-22-1621502920702] - >> Procuring relationship types from cmdb_rel_type - measuring time...

Integration point is properly configured, and WSS connectivity towards the Service Now instance is OK (tested via the "test connnection" button). So it is really the Integration adapter itself that does not start, even when using an OOTB Integration query such as Windows Push 2.0. 

What strikes me are the two "strange" entries in the fcmdb.push.all.log :

2021-05-20 11:28:40,767 DEBUG [AdHoc:AD_HOC_TASK_PATTERN_ID-22-1621502920702] - >> Loaded setting PushConnector.skip.mapping = 'null'

and a bit further

2021-05-20 11:28:40,876 DEBUG [AdHoc:AD_HOC_TASK_PATTERN_ID-22-1621502920702] - >> Attempting to load properties file from: []

Small detail : when we select a query which does not get any CIs in it, then the adapter is working fine (but do nothing, as there is nothing to push to SNOW anyway).

Any of you did already encounter this kind of issue ? 

Thanks for your help.