If you're still stuck in a group after re-logging, you can try reforming the group you were in when the issue occurred and then disbanding it. You can also try joining a large group and asking the group leader to disband it. This can help reset your UI. To prevent this from happening in the future, we recommend not logging out of the game while still in a group.
If you're still stuck in a group even after re-logging, you can contact customer support for further assistance.