Do you also get similar message when login to UCS manager? What is the domain name you are using? There is a 32 character limit in UCSM for username. As per document
"For systems using remote authentication protocol, the authentication domain name is considered part of the user name and counts toward the 32-character limit for locally created user names. Because Cisco UCS inserts 5 characters for formatting, authentication will fail if the domain name and user name combined character total exceeds 27"
The UCS Central document also mentions this limit but only for RADIUS authentication.
"For systems using RADIUS, the authentication domain name is considered part of the user name. Therefore, it counts toward the 32 character limit for locally created user names. Because Cisco UCS reserves five characters for formatting, you cannot have a combined total of more than 27 characters for the domain name and user name"
