It might be caused by the Salesforce outage.
https://www.theregister.co.uk/2019/05/17/salesforce_database_outage/
https://status.salesforce.com/incidents/3815
Impacted Services
Core Service
Additional Information
We continue to work on restoring access and permissions for customers affected by the permissions issue. During the restore process, some affected customers may receive error messages related to account status, billing, or single sign-on functionality after logging into Salesforce. There is no action you need to take if you receive these messages. We will update you with additional details and information on this situation as they become available.
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