Release : 4.9
Component : CA Test Data Manager
Issue is happening when the JWT token length is huge due to the huge list of access permissions assigned to the user. (huge HTTP request header size)
Review this documentation link:
https://techdocs.broadcom.com/content/broadcom/techdocs/us/en/ca-enterprise-software/devops/test-data-management/4-9/administrating/ca-tdm-portal-administration/ca-tdm-portal-troubleshooting.html#concept.dita_9470b0b4a38c9e4ddddc8fdd6f7dce6b4e7c1843_tablesize
Set the "maxHttpHeaderSize" attribute in the Tomcat server.xml to a value of "3000000" (include quotes) and restart the service.
This resolved the issue.