I cant join any servers or play with friends.

I will try to get on servers and it will say that the server is down for maintenance but I check and the server is join able When i want to play with friends, they will open to lan will im close to the host and i cant get on. Nothing pops on my screen! I have no idea what is happening, i used to be able to play with friends/servers , but now i cant please fix or tell me what to do.