Lol does it actually say that? I cant get into my old account on the forums because my old email has been deactivated for some time now and Im in the process of getting it changed.
A vast majority of the playerbase seems to run the game on Minimum anyway. They also seem to prefer spending their money on Armas weapons than getting/building a PC that isnt a complete potato. Seriously, I built my rig from a summer job (with rent, insurance, car, food, the usual expenses) and it runs Arma 3 maxed out at 160+ FPS. I don't see why minimum graphics are even an option now, if you can't run APB at this point, then why even bother having a PC?
Usually it's because the servers go down. In your case I'd say either your network (router) has blocked the connection to the servers, or your internet quality is somehow so poor that it doesn't allow you to enter the game.