I know this is old but I encountered this issue when trying to set up a second depot and workspace for a new project and thought I’d leave my solution here for anyone googling
The problem for me was that my workspace name didn’t match my workspace path. You can check whether they match or not by going to Workspaces tab > Right clicking your workspace > “Edit workspace”. Then right click on the depot you are trying to use and click “Include special”. This will open a new window that shows you the workspace path. If the two entries don’t match you won’t be able to submit files.
All I had to do was manually remove “/Voxel” from the workspace path:
After that I was able to add files without “files not in client view” error.