If you get the error message: Cannot login: Invalid user name/password or tenant id, then the obvious reason might be, that you are using the wrong password or user name.
Another thing that might prevent you from signing on if you are using https is a certificate, that has expired. If that is preventing someone from signing on, then you can see that in the interformng2_audit.log file.
You can find the file in this default path if you are running InterformNG2 on Windows:
C:\ProgramData\InterFormNG2\profiles\default\logs
(You may have configured another path in the environment variable, INTERFORMNG2_HOME.)
On the IBM i platform you can find the file in the IFS in the directory:
/iformng2/InterFormNG-shell/user/profiles/default/logs
Inside you might see an error message like below if the certificate has expired:
Caused by: java.security.cert.CertificateExpiredException: NotAfter: Day Month xx hh:mm:ss yyyy
You can refer to this section
HTTPS enabling for how to install a new certificate to solve the issue.