Failed to Save

This is a 1st for me, I’m working on a converted model from AutoCAD and after changing a few things and saving a couple of time OK I am getting a “Failed to save Document” message.

I’ve tried to save in a different file and under a different name. no luck.
What could this be about?
Failed to Save

Where was the SKP model file located when you opened it?

• On local drive C:
• Some place other than C:

it is on my my local drive “D:” a solid state drive on my computer.
Some of my later attempts to save the file was to my desk top before it crashed.