Processes in Microsoft 365 for setting up Office apps, redeeming product keys, and activating licenses.
Office themes can also be set through a registry key, so that may be something else to try. I was also missing the Black theme and was able to set it through the key.
- Search for the Run app (or press Windows + R) to open a Run window.
- Type "regedit.exe" in the search bar and press "OK" to open the Registry Editor.
- Navigate to "Computer\HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Common". Here you'll find Office registry keys for settings used across the Office suite.
- Double-click on "UI Theme" and change the "Value data" to 4, the Black theme equivalent (3 is Dark Grey, 4 is Black, 5 is White, and I believe any other value will default to Colorful).
- Restart any running Office apps to see the updated theme.
If you go back into File->Options in an Office product and check the theme you've set, it may appear blank. You should be able to set it to any themes you were able to see previously but any hidden theme will still not be in the list.
Hope this helps!
Natalie