It seem that this error is new in recent versions of Insync:
Syncing for <folder> is paused because it went missing
We’ve had Insync running for multiple years on these folders and we’ve only recently begun to see this error.
FYI, we’re running on Windows 7 Pro x64. We have 8 folders where this is happening. The folders in question are actually all on alias disk drives set up using the Windows SUBST command.
At this time I also want to renew multiple user requests for Insync to provide user controlled settings to allow email notifications for all Insync events requiring user intervention. In the case of this error (Syncing paused), we have no idea how long the syncing was paused. We only happened on the problem. We’ve seen the same problem from incoming files as well. Please, please, please implement email notifications ASAP. This simply can’t be that hard and this feature will close a significant gap in the reliability of Insync.