If you see this screen when you are testing your SAML setup then it may be caused by trying to login as a different user roles using Salesforce's "login as" feature.
This won't work for testing
Going to the Users screen and clicking "Login" to login as a different user will not work for SAML testing. You will get the error seen above. You will need to either:
- Have the user with the role you want to test actually login to Salesforce and test it on their own
- Change the role of your own account to test