This article was created in response to a support issue logged with K2. The content may include typographical errors and may be revised at any time without notice. This article is not considered official documentation for K2 software and is provided "as is" with no warranties.
You are unable to add new users to any OOTB role because only the K2 Service Account is a member of the security administrators role.
This is a known issue that prevents adding users to Roles.
This has been fixed in K2 Cloud Update 5 FP1.