Hi Brogan, my style is compatible with 1.2. I also tested whether it works with the default style but it doesn't. I have also disabled all add-ons. I have Super Admin permissions.
That's it. I was only an admin not moderator. I am now, so it is working. Thank you for the solution.
One more question. My forum moderator permissions were put into moderator groups. So if I have to promote a member to moderator, I would change his / her usergroup. With Xenforo, does it work differently? Are these usergroups are not necessary now?