Thank you Michael for the tips, even though this is likely not a MoI problem.

Rhino 8.1 not installed at home yet. It is funny that the preview problem showed up on Windows 10 pc, and Windows 11 pc, about the same time.
Will upgrade 2 SSD's in a few days.

I recently purchased a "baby" Dell pc for CNC, with nothing loaded yet, (Windows 11).
I'll install a few things and see if preview gets messed up or not, and report back later if anything turns up.
(I only use MoI on one computer at a time.)

- Brian

So MoI thumbnail viewer only works for recently saved .3dm's???

Loaded existing .3dm into MoI5_Dec1 Beta, and saved to D drive,
and to MoIAppData. They were the AlibreLogo.3dm and an Acorn.3dm
Preview works on them. (They currently show a file type (Icon) of Rhino.

.htm and .js still do not preview, but try to load.

T-Rex.3mf DOES preview.

- Brian

Explored some mysteries of OneDrive...

Will Checkout Rhino vs MoI .3dm preview...

Hi Brian,

re:
> So MoI thumbnail viewer only works for recently saved .3dm's???

It should work on any .3dms saved since the Mar-28-2023 v5 beta which is the first version of MoI that would save thumbnail images inside .3dm files.

- Michael