I have a multi account organization with AWS SSO. I messed with securityhub a while back ago and would be able to enable/disable it. A year later I tried using it again but I cannot get into it. I've tried accessing it with my root account, and even created a full access IAM user to test outside of SSO and that doesn't work either. I get this same issue with GuardDuty too. I don't have any SCP's that would be blocking this, and I've tried using the AWS provided securityhub policies too.
What else would be blocking access to securityhub?
In this particular case, my system clock was off and was resolved by enabling a time sync setting. If all permissions look good, this error can prompt because of a system clock issue as well.