In DLP 26.1 changes were made to the security and authentication framework. It's important to review the authentication configuration in the Enforce server Manager.properties file after upgrade to ensure the correct settings for your environment.
DLP 26.1
Refer to the Security and Authentication Framework Improvements section in the Platform Features in DLP 26.1 TechDoc:
In DLP 26.1 the authentication settings have been moved from the springSecurityContext.xml file to the Manager.properties file, upon upgrading DLP, Administrators should review these settings to make sure they match authentication requirements for the DLP environment.
Please review the TechDocs regarding authentication configuration starting with the Enforce Server Authentication TechDoc page.