Video posting is disabled by group settings
Social media platforms allow administrators to set content posting parameters in groups. In some cases, video posting may be disabled, leading to an error when trying to post content via Postmypost.
Possible causes
The group settings have disabled the ability to post videos.
What to do?
Open the group settings, check if video posting is allowed, and if necessary, enable this feature.
See the detailed instructions «How to enable video support in a VKontakte group?».