unable to add user to group fedora 29

I used groupadd to add a group so that I could manage with git some root owned scripts. I then used usermod to add a user to a group. The user is the currently logged in standard user and I am in a shell through su into the superuser account in the terminal. I logged out and logged back in again, having run sudo usermod -aGgroupname username as I always have done. After I logged back in as the standard user, the command groups continued to show just the user, but when I logged in to the superuser account and ran groups stdusername the output showed that the std user is a member of the new group. I don't understand how this can happen.