We have ArcGIS Server 11.5 on a RedHat Linux 9. It was connected to MS SQL Server 2022, also on the same. Linux server.
I am accessing the service from my windows 11 desktop running ArcGIS 3.6 Pro.
I tried to publish a simple map service of a WGS1984 map, with 12 feature layers, that, together comprise a comprhensive base map for our project.
Upon analysis, I got this message:

The database is already registered, so i tried a few things to no avail.
I finally tried to reregister the database, using my local connection file, and got this message:
Things should be easier than this.
I am able to connect to the database using sde from my ArcGIS Pro. I am also able to connect to the ArcGIS Server from my ArcGIS Pro.
The feature layers I am trying to publish are using tables from the ms sql database, and these table have been turned into FeatureClasses inside sde on the ArcGIS server.
I also did what turned out to be a foolish thing, which was to deregister the database using Server Manager and trying to reregister it. I used the connection file from my windows 11 machine.
I now get this:

Its the same error at all three attempts.
Any guidance would be appreciated.