ConnectBooks adds custom fields in QuickBooks Desktop, like the Group ID. QuickBooks has no custom fields left, so ConnectBooks can't add the one it needs.
How to fix it
Pick one:
In QuickBooks Desktop, remove a custom field you no longer use.
Or stop ConnectBooks from adding custom fields for this store. Go to Stores & Files and click the store. On the Accounting tab, under Accounting Settings, click Settings. On the QuickBooks tab, click Configure Advanced Settings. Untick "Create Custom Fields in QuickBooks Desktop for Group ID etc." and click Save.
Then, in QuickBooks, click File, then Update Web Services. Tick your company and click Update Selected.
Frequently asked questions
Which option should I pick?
If you use your own custom fields in QuickBooks, untick the ConnectBooks setting. If you have a custom field you don't use, remove it.