Error “Workflow was unable to authenticate this request. Detail: Token could not be retrieved; retries exceeded the limit”

Issue

When an Office 365 workflow runs after a task becomes overdue, the following error might occur:

Error Code

Error “Workflow was unable to authenticate this request. Detail: Token could not be retrieved; retries exceeded the limit”

Resolution

Ensure that the task escalates to a valid user or group account:

1. Open the affected workflow in Nintex Workflow Designer for Office 365.
2. Double-click the Task action that caused the workflow suspension. 
3. Navigate to "Escalate and auto-complete options".
4. Check the value from the field "Escalate to".
5. Ensure this User or Group exists within the SharePoint Online environment.

1. Go to Site Setting > People and Group.
2. Find if the user or group from this page. 

6. If the User or Group does not exist, either create this account or update the Task action to escalate to a valid account.?