We experienced this as well after Windows Server patching/updates. Data Store service is running, validates with ArcGIS Server, hosted services are started, but they do not load in Portal's map viewer nor in ArcGIS Pro.
Running the describe data store utility did not show anything out of the norm. Restarting the Data Store service did not resolve.
Fix: Reboot ArcGIS Enteprise components in this order:
Stop: Data Store, Server, Portal
Wait a few minutes
Start: Data Store, Server, wait a few minutes, Start Portal, wait a few minutes
This allowed hosted layers to work in Portal now. In ArcGIS Pro 3.1 and 3.2 we had to start with new Projects for the hosted layers to begin working. Existing maps continued to show the same errors, even after re-adding layers/updating sources.
Also wanted to note: This outage has happened twice before. In those instances we ran the Configure ArcGIS Server account and input the same credentials we had used before, and this also solved the issue. Rebooting windows services fixed it for us in this instance but the configure service account might be something to try if that doesn't work.