Limits on 'Add to a group'

There's sometimes "Certain groups may not appear" notice given when adding the group contributions. The explanation opens from the question mark. For example adding anything else but still images is maybe defined on number of groups, and the notice is given when trying to add for example a video file as a contribution.

Moreover, some groups may have closed the contributions, either permanently, or temporarily. For example the Fence Friday group sometimes closes the contributions for few days.