This issue is commonly caused by the FinOps users being disabled.
To check this:
Login to FinOps Administrator
Browse to System Control, Users
Ensure that the affected user has a tick in the Enabled column
If they do not, click Edit (hand with a question mark icon) and tick the user as required
Click Save (green tick icon) to save the changes
If this doesn't resolve the issue, please raise a new case online and reference the title of this article and include details of the user affected.