Hey everyone,
I had a power cut at home during a zorin update which forced me to completely reinstall gdm and zorin-desktop. The problem is that now I can't change zorin's appearance 
If you need more information, don't hesitate to let me know.
Any help can only be useful 
Welcome to the Forum!
Try to reinstall Zorin Appearance and the Layouts with the following Command:
sudo apt reinstall zorin-appearance zorin-appearance-layouts-support zorin-appearance-layouts-shell-premium
Hello, thank you for your quick reply, but unfortunately your command doesn't change anything. I don't get any error when I run zorin appearence with the terminal. If you need a log file or anything else, don't hesitate to bother me 
Does Your Desktop has the normal Zorin Taskbar and Startmenu or is it complete empty?
I have a small update. I executed this command: sudo apt remove --purge zorin-appearance, then sudo apt install zorin-appearance. Now, I have a message suggesting that I upgrade to Zorin OS Pro, even though I already have the Pro version. Moreover, it no longer shows me the other themes.
sudo apt install --reinstall zorin-appearance-layouts-shell-premium
I had tried this command, but unfortunately, it didnât change anything :â(
Did you try it before or after this action? ^
I tested it before the uninstall command, and I tried again when you advised me to.
And terminal shows nothing after running it?
Have you rebooted?
I restarted but nothing happened, here is the output of your command:
theo@zorinos:~$ sudo apt install --reinstall zorin-appearance-layouts-shell-premium
[sudo] Password for theo :
Reading package lists... Done
Build dependency tree... Done
Read status information... Done
The following packages have been installed automatically and are no longer required:
gir1.2-camel-1.2 gir1.2-clutter-1.0 gir1.2-cogl-1.0 gir1.2-coglpango-1.0
gir1.2-ebookcontacts-1.2 gir1.2-edataserver-1.2 gir1.2-folks-0.7
gir1.2-gdata-0.0 gir1.2-gee-0.8 gir1.2-gsound-1.0 gnome-themes-extra
gnome-themes-extra-data gtk2-engines-pixbuf nvidia-firmware-545-545.29.06
nvidia-firmware-550-550.107.02 sshfs
Please use âsudo apt autoremoveâ to remove them.
0 updated, 0 newly installed, 1 reinstalled, 0 to be removed and 2 not updated.
It is necessary to take 5,856 o from the archives.
After this operation, 0 o of additional disk space will be used.
Received :1 https://packages.zorinos.com/premium jammy/main amd64 zorin-appearance-layouts-shell-premium all 4.0 [5.856 B]
5.856 o received in 1s (5.994 o/s)
(Database reading... 302495 files and directories already installed)
Preparing to unpack .../zorin-appearance-layouts-shell-premium_4.0_all
.deb ...
Unpacking zorin-appearance-layouts-shell-premium (4.0) on (4.0) ...
Setting up zorin-appearance-layouts-shell-premium (4.0) ...
theo@zorinos:~$
I don't know if you need more information ?
It should be showing... You may need to contact the ZorinGroup directly on this one and see if they have a moment to help...
There is a Pro support "Contact Us" form:
Dedicated support from the ZorinGroup applies to Installation Support Only. So those seeking assistance with installation will get first priority.
You can make the case that you seeking installation support of the premium layouts. 
Ok, thanks for your help, I'll go ask them directly if they have a solution, have a nice evening 
So, the Premium Layouts are showing - even if not available ... Maybe You need the Core Layouts seperately. If yes, then this would be my fault because I don't list them. I thought they would be integrated in the Premium Layouts. And because You have the Pro Version, I thought that would be enough.
So, for the Core Layouts type:
sudo apt reinstall zorin-appearance-layouts-shell-core
If the Reinstall shouldn't work, try it with an Installation:
sudo apt install zorin-appearance-layouts-shell-core
No, unfortunately the commands you gave me don't change anything, but when I asked chat gpt for help, it gave me the name of a file (/etc/zorin-os-pro-license) that I don't have on my pc. Do you think it could be linked, or is he talking nonsense?
I don't have the Pro Version. So, it is difficult to say something to that. But because of Your Picture with the Pro Layouts and that they not active, it could be that something with Your Pro Licence is maybe problematic. But for this you should maybe ask the Zorin Support that @Aravisian has linked for You.