There are 2 web adaptor,
one is portal adaptor, one is server adaptor
Subject 1. server web adaptor
How to login arcgis server admin directory ( not arcgis server manager )
option 1. use arcgis server admin account to login
option 2. for federated server, you can generate portal token login without arcgis server admin password.
https://gis1.victorvilleca.gov/arcgis/admin/
You only have 1 arcgis server web adaptor, but you seeing 2 item here is because ....
1.1 public facing, use domain name
1.2 internal only, use full machine name
Subject 2. portal web adaptor
You should have 2 account for your enterprise portal.
One is portal admin account,
one is portal service account.
Portal admin account is used everywhere except during the process of installing or upgrading portal.
Portal service account only used during the process of installing or upgrading portal.
Login to portal admin, by using portal admin account
https://gis1.victorvilleca.gov/portal/portaladmin
click system
click web adaptor, click machine name
how to unregistar it
2 web adaptor is in different color
Check whether your 2 web adaptor is ok,
/arcgis/ is for arcgis server web adaptor
/portal/ is for portal web adaptor
