I had an issue with the InDesign-Files on our HiDrive-Server. They all became read-only over night, if you open them in InDesign. You also could not save a new file from InDesign on the server ("File is damaged")
I found the solution together with the 1a-support from HiDrive. I thought it might be a good idea to share problem and solution here.
The server was connected via WebDAV. The problem occured since Hidrive changed something in their security settings. The solution is to change from WebDAV to SMB.
If you can't connect to a SMB-Server in the Finder you may have a router that enables a NetBIOS-Filter by default (like the FritzBox does). Disable the filter in the General Filter Settings and you can mount SMB-Server via the Finder.