That is the problem with wireless it can work fine one minute and then be unusable the next. It is affected by any number of things. It can be as simple as someone closing a door and changing the reflection patterns in the house.
It really doesn't mater your options are still the same you need to find a way to avoid whatever interference is causing the issue. Since it is impossible to actually see you just are pretty much stuck just randomly changing the few things you can.
This is the key reason the recommendation is to use ethernet cables for playing online games. It is a massive issue and there is no real fix, the way wireless is designed is the worst possible option when it comes to what games need to run. Now it works...