Sorry to hear about this issue.
Sharing annotations with groups works on a per-annotation rather than a per-document basis. What this means is that all of your annotations that you wish to share must have the “my groups can see annotation” box checked.
Also, when you check that box on an annotation and click save, it only shares with whatever groups are currently attached to the document. So, since you added a group to the document after making the annotations, you may have to do the following for all annotations: edit the annotation, uncheck the box, save it, recheck the box, and save it again. That will ensure that each annotation is visible to the group that is attached to the document.
You can quickly see which annotations are visible to your group members by toggling the “Mine/Groups” toggle at the top of the annotations list. In “Groups” mode, you can see which are visible to your group members, while in “Mine” mode you can see all annotations you have made. You can tell that you have shared all of them when all Mine annotations show up under Groups.
Apologies for the inconvenience. We are looking at bulk actions for the next major version of Annotation Studio, which will hopefully make such problems easier to solve.
Annotation Studio Team