Why can't I sign in to Dynatrace using single sign-on (SSO)?

[MalcolmDavidson]

Dynatrace allows organizations to use their corporate credentials for authentication to Dynatrace.

If your organization has SAML federation configured and you experience issues signing in, inform your administrator about the issue and confirm that your organization's SAML SSO configuration is correct.

[ChadTurner]

Also don't forget, If you are having Issues logging in after the end of February, its most likely because the Certificate expired and you need to add in the new one. 

https://docs.dynatrace.com/docs/manage/access-control/user-management-and-sso/manage-users-and-group...