I can confirm I'm having a similar issue, and can provide more specific conditions:
a) using the desktop version of Draw.IO
b) using Google Drive File Stream integration
1) Create new Draw.IO diagram
2) Save to Google Drive via File Stream (filesystem op instead of GD API op, probably can't/doesn't provide appropriate metadata to GD)
When looking at the
draw.io files in Google Drive through the browser thereafter, it does not recognize the files as Draw IO diagrams. There was one FAQ suggestion to rename/append .xml, save, and then remove the suffix, but this doesn't seem to correct anything. Having the .xml appended
does make Google Drive
suggest Draw.IO as an application, but the diagrams still fail to produce a thumbnail or rendering.
Hope this helps! Would like to see this resolved. It also makes sharing diagrams problematic.
Thanks,