Check if you have a folder call "mods" within your game's folder.
Then within that, check if you have ANOTHER folder called "mods" (so it's mods\mods)
If you have a folder mods\mods congrats, you are the victim of poorly coding by the modder maintaining the plugin in vortex for 7 Days to Die that doesn't allow you to ever .
To fix this:
0. Close vortex (make sure it's shut down)
1. Copy paste this in your explorer's address bar to open the game's launchersettings.json file:
%appdata%\7DaysToDie\launchersettings.json
If windows asks you how to open that file, select "Notepad" or any text editor.
2. Modify the line:
"AdditionalParameters" : "-UserDataFolder=D:\\Steam\\steamapps\\common\\7 Days To Die\\mods",
to
"AdditionalParameters" : "-UserDataFolder=D:\\Steam\\steamapps\\common\\7 Days To Die",
3. Restart vortex, purge all mods, then re-deploy them.
The mods will now be correctly installed under "7 Days to Die\Mods" instead of "7 Days to Die\Mods\Mods"