The inspection portal gives the reason of the AG error when clicking on the icon.
This example shows an invalid VIN. The message states '(VIN) string does not match regex'.
To fix this we want to confirm the correct VIN, which can usually be done by viewing the photo of the VIN sticker. (Shown above) Then we go into AMS -> Function -> Vehicle -> Inventory Management and update the VIN section on the 'Vehicle' tab. Once saved you can refresh the page in the inspection portal which will update the VIN and correct the error.