System error: 401 unauthorized error

A 401 unauthorized error indicates that the user who connected SOS Inventory to QuickBooks Online is no longer an administrator for QuickBooks Online, or that the access token granting your connection to QuickBooks has expired. To fix this problem, an SOS Inventory user who is an administrator for both SOS Inventory and QuickBooks Online should take the following actions:

1. Log in to SOS Inventory.
2. Go to Settings > QuickBooks setup.
3. Disconnect SOS Inventory from QuickBooks Online.
4. Reconnect SOS Inventory to QuickBooks Online.

Syncing should resume without a problem. Contact Support if the issue is not resolved.