When you have given the new user the correct permissions within the K2 Management page, the user is unable to open up the swagger definition and cannot log in with the credentials provided.
The following error appears:
"Authentication With Server Failed: Logon failure: the user has not been granted the requested logon type at this computer"
To resolve this, you need to add the user under the local security policy. You can navigate here by following this path:
Start menu > Local Security policy > Local Policies > User Rights Management > Log on as Batch Job
When completed, the user should be able to open up the swagger definition as expected.