I have problem when create new portal with Portal for ArcGIS 10.6, always error while using OS Linux CenTOS 7.5 and Linux Ubuntu.
There was an error creating your initial administrator account.
Unknown resources - could not find token service endpoint
I already checked the log and found some errors with the database like this,
PDT: : FATAL: no pg_hba.conf entry for host "[local]", user "arcgis", database "arcgis", SSL off
FATAL: role "arcgis" does not exist
have the same issue - it points at the initial administrator account and the SSL off shows up on machines in the network as an https:// error in the browser (2nd clue) - this is in Windows Server after repairing the ArcGIS Portal install.