If you are unable to access Solomon but have been granted access. 

1) Make sure you can login to the MISO public website. (The logins are tied so if you can login to the MISO website you should be able to login to Solomon.) 
2) If you still can't access Solomon, take a screenshot of the error message and submit this with your ITOC ticket.

This will help streamline your issue as the error message should be on the screenshot.