Insync has undergone a major re-write of the underlying sync frameworks from version 1.5.x to 3.0.x.
Integration with file managers like thunar is a work-in-progress with this new version. More troubling is a major change in sync behavior with the series 3 version. While the new version has many more syncing options, there is a significant change that is NOT adequately explained.
Previously, all files in the sync folder were synced across google drive and the computers connected via Insync UNLESS you selected parts of the folder/directory for a manual or no sync.
With an upgrade to version 3, however, all files on a computer are synced with google drive, but new files created on one computer are no longer added to other computers connected to google drive via Insync. As a result, folders across computers will get out of sync with each other, which kinda defeats the whole purpose of syncing software for most folks.
Here is what you will see when examining an un-synced folder from within Insync:
In this Employee folder, there are numerous files that are NOT synced on the particular computer on which Insync is running. These files were added on another computer and synced to google drive. But, the files are NOT synced automatically to other computers unless I now tell Insync that I want these files synced with this computer.
To fix this problem, on each computer you need to go to that folder from within Insync and then select the cloud selective sync option:
You then need to select the folder (or file) you want to sync on that computer:
Then, click on the green Sync button, and the contents of that folder and all sub-folders will be synced on that specific computer:
This process needs to be done on each computer and for every folder that needs to be synced across those computers.