This would be something for Adobe to investigate and get back to us with the details. It is mostly related to one of the Adobe internal errors. Please reach out to Client Care with the following details:
1) Since when have you seen the error?
2) Is it occurring across all the Workspace projects?
3) Are other users seeing the same behavior?
4) How's the behavior on a different browser/machine?
5) Is any error seen in the developer console of the browser?
Seems, it is because of Adobe maintenance but not sure, do you see this issue consistently not going off
Recently I see this issue and after some time it automatically away, but now when I generate reports in the workspace I see again. But after some time by changing the date and click on the apply button it is working.
If it does not go away, you can check below link to submit a support ticket