Please check if you have enough disk space on the drive that you’re saving to. Also that all administrator privileges are correct. Perhaps try saving to the desktop to ensure that your computer is communicating with the drives.
Do you save on a server?
Try it local. And move it than on the Server.
Don't save using the same name. Increment the name. Call it "Project_01" instead of "Project" where you are required to save over the original file.