MC_Luca5

"Forge Mod loader could not connect to this server." Someone told me to downgrade Attack of the B-Team, but it still won't let me join

I had this mod-pack before. I reset my computer because it was running slow and then I had to reinstall everything. I tried to reinstall Attack of the B-Team and join a server and it said that FML could not connect to the server because I was missing a lot of mods. I checked on another server to see if it was just that one server, but it said the same thing. I am confused to why it is not working! PLEASE HELP ME