When you go to the filters, go to advanced settings and see if changing your region there will help as well as see if you have marked any other region by accident and if yes un-mark that.
Also, do note that servers depend on the server owners and if they what to maintain them. You may sometimes find your favorite server missing simply because they no longer exist due to the server owner. Not saying that there is zero of this region servers out there but if you are looking for your older ones it could be the case.
As a tip, if for some reason it refuses to give you any servers all the time, if you have any friends and they are playing on such servers join in on them and that should work as a temp workaround. Sometimes the filters get messed up but usually fix themselves in a selected time so this workaround could be good to be used in the meantime till it happens.
