I just wanted to look in FL after a few years of break again, when I only connected for account holding. I never had any problems with the Launcher until today. Every times I start the launcher I get an Scripterror window on top of launcher. This one is automaticly filled in German by my German Windows 10 - so it is not a normal exception of yours (at least I admire that your coding is not German) but a native one catched by system making it even more strage. There it is (translated) said that at line 12 char 122 an unknown runtime error is thrown at URL "about:blank". I can react to this msg with yes ot no but both ends with the launcher is being closed.
I also thought about just reinstalling game and mod totaly but I am in fear about losing the account. Like I said I haven't played for a long time so I am not sure if my old backup of ids is still up to date so I decided you ask you for support first. OC I would prefer an repair of the existing to a reinstall if you have an idea but an error like this seems to an informatican like me as unrepairable without reinstalling .
At least the Launcher does not fail completly as it sees that a patch is needed so a general connection to server was established before the runtime error occured.