Hey @sigxo
The videconfig file is located in this directory: %userprofile%\saved games\respawn\apex\local
If the previous folders or the file itself is set to read-only then it will not be able to save changes made in-game, so it's recommended to make sure it's not read-only.
Though if that's not the case, the best thing to do is probably to back up the file and delete it from that directory to let the game generate a new one.
After a new one has been generated you can simply copy over the contents from the previous videoconfig file.