Reported on IDM 22.214.171.124, also reproducible on IDM 126.96.36.199. Does not affect IDM 6.5.0.
IDM 6.0.0.x with external DS repository.
If IDM is configured to use SSL (in repo.ds.json):
IDM connects to DS using TLSv1.
This appears to be due to this DS bug that was fixed:
OPENDJ-5553 : Rest2Ldap cannot connect to TLSv1.2 servers
The bug is fixed in DS 6.5.0, and 6.0.1.
IDM 188.8.131.52 is using opendj-core-6.0.1-M2.jar, which does not include the fix.