I still don’t understand why, but InSync decided that my root Google Drive folder was empty and deleted all of my Google Drive files.
They were moved to Trash, so I technically could undelete them. Except that for 387GB of files, the interface doesn’t work. That forced me to use an AppScript script to undelete everything, but now the original folder structure is gone. So I have 387GB of files in one folder and absolutely no way to recover them.
InSync this was your one job and you have failed catastrophically. I regret ever using your software, let alone paying for it. I hope everyone else takes extreme precautions.