Error: 18456, Severity: 14, State: 11. Login-based server access validation failed with an infrastructure error
Check the new endpoint name on sys.endpoints table and grant connect permission for the user. The new endpoint name should be different from "TSQL Default TCP".

Use this script for windows login:

GRANT CONNECT ON ENDPOINT::"NEW_ENDPOINT_NAME" TO [DOMAIN\firstname.lastname]


Or use this for sql authentication login:

GRANT CONNECT ON ENDPOINT::"NEW_ENDPOINT_NAME" TO "username"