Unable to connect to data source - Login failed for user 'NT AUTHORITY\ANONYMOUS LOGON'

Question

I found a number of posts about this here and elsewhere. I think I have followed everything correctly, but I'm still getting the error. So obviously I'm missing something.

Running SQL Server 2019. Domain functional level is 2016. SQL server is running Windows Server 2019 and the SSRS server is running Windows Server 2022.

I have two servers, we will call them SQLSRV and SSRSSRV. Both exist on the same subnet. On SSRSSRV I have it configured to run the service as an AD account. I can see entries have been made in SQLSRV regarding permissions for that account in the report database. Originally, no SPNs were registered. So I have added them and have the following now:

> setspn -l DOMAIN\ssrs_user
Registered ServicePrincipalNames for CN=ssrs_user,DC=DOMAIN,DC=local:
        http/SSRSSRV
        MSSQLSvc/SQLSRV:1433
        http/SSRSSRV.DOMAIN.local

I tried adding the FQDN for the SQLSRV as well, but it saw that as a duplicate and didn't add it.

In ADUC I have verified that "Account is sensitive and cannot be delegated" is NOT checked. And in the Delegation tab, I have set it to "Trust this user for delegation to any service (Kerberos only)".

In rsreportserver.config, I have tried setting AuthenticationTypes to all three values RSWindowsNegotiate, RSWindowsKerbero, and RSWindowsNTLM. Also tried all three at once.

I have restarted the SSRS and SQL services after any changes.

In SSRS, under my data source, the connection string is:

Data Source=SQLSRV; Initial Catalog=MyDataBase

And when clicking test, I get the error saying:

Couldn't connect
The report server couldn't connect to the data source using the information you entered. Make sure you've entered the connection string and any credentials correctly.

Hide error details Login failed for user 'NT AUTHORITY\ANONYMOUS LOGON'.

Additionally, I verified I can connect to that SQL server and database using my current account without issue using SSMS.

I am able to connect to the datasource in SSRS using local SQL account. It also works if I set it to use specific Windows credentials. But I need it to work with the current user's permissions.