Cannot connect to server means either the server is full or it is down. Give little time when it shows logging in like for a minute or 2, you will be in.
Bonus 50% EXP!
Double Money Gained!
Access to Members Only Areas
Early Access to various Pokemon!
Access to unique Members Only Clothes, Hats and Mounts (From various Quests and Shops ingame) (This is not the Coin Shop)!
Can't connect to server means either the server is full or down, and the game is on so keep trying and you will login as we have expanded the server cap to 1100.
This doesn't explain much, can you give more details like what level was your Pokemon and the wild Pokemon level and where did you not get Exp after fainting a wild Pokemon?