Fix SSRS Data Source Issue

I need assistance with an SSRS report that's failing due to a data source connection issue.

Details:
- The report is connected to a SQL Server database.
- The error encountered is an authentication failure.

Login failed for user 'NT AUTHORITY\ANONYMOUS LOGON'. Reason: Token-based server access validation failed with an infrastructure error. Check for previous errors. [CLIENT: 1.2.3.4]
Error: 18456, Severity: 14, State: 11

Ideal skills and experience:
- Strong expertise in SQL Server and SSRS
- Experience troubleshooting data source connection issues
- Familiarity with authentication mechanisms and resolving related errors

Looking for a freelancer who can quickly diagnose and fix this issue.