"Save As" not working properly

I have been using Rhino 7 on a PC for a while. After working on files and changing them - save as always worked. Suddenly it stopped and I get a message “Failed to save Rhino 7 file E: (file name here). Writing to the disk or storage device failed”
I have tried “Importing Selected” and “Save” with the same result. I closed down all programs and reopened the computer and still have the same problem. My external drive is only half full.

Have you been using an evaluation license and the evaluation period expired?

Run the Rhino command SystemInfo and post the result here.