Why is this happening?
This error may occur when adding a new matter when synced with a document app.
How to fix this error
- Go to Setup > Apps > Turn OFF the document app that you have turned on
- Go back to matters page > Click Add > Save the new matter.
- After the matter is saved, go to Setup > Apps > and Turn the document app back on.
Related Article: Error: Cannot Create File or Folder (When Adding a New Matter)