A sytem error has ocurred 400. HTTPS System Error

[Nekody]

Since today I've been getting this error every time I open the FFXIV launcher. Nothing has really changed in my PC, and I've tried everything. I've found other threads about this error but they are all from more than 4 years ago, and the solutions these threads recommend doing haven't worked for me.
The error looks something like this:

I've really been struggling for hours trying to fix this thing, but I can't seem to find the solution.
Please, if someone knows anything about this error, help me. I really love this game and I want to be back playing as soon as possible.
Thanks.