https://www.gog.com/forum/elder_scrolls_series/you_can_free_up_to_12gb_in_your_skyrim_installation

Just out of curiosity, did you deleted Skyrim - Voices_en0.bsa or any other localization files using this method of freeing up space in your Skyrim installation folder?

In any way, I suggest you look up in those paths if nothing else works:

Path 1:

0) Go to \Documents\MyGames\Skyrim Special Edition GOG\

1) Rename your Skyrim.ini and SkyrimPrefs.ini to Skyrim.ini.BAK and SkyrimPrefs.ini.BAK

2) Relaunch your game through 'SkyrimSELauncher.exe' in your installation folder - that should create new ini files that might have wronged configurations

3) Check if it did created new ini files at \Documents\MyGames\Skyrim Special Edition GOG\

4) If yes, start the game and test it.

Path 2:

0) Go to \Users\%YourUserName%\AppData\Local\

1) Are there two folders with the names "Skyrim Special Edition\" and/or "Skyrim Special Edition GOG\" ?

2) If yes, open both and check if there any configuration files (.ini or .txt) inside them

3) If yes, rename them the same way with ".BAK" at the end

4) Open your game through the launcher the same way as first try and check if it's working