Try selecting tools in the menu bar, then clicking network. When the network settings windows opens uncheck "select server automatically" and keep trying different servers in the list. Sometimes a particular server is out of sync with the blockchain, and switching to another fixes that.
Also your firewall might be blocking electrum from accessing the internet.
Search for your address in this website to find out if its already been sent coins. If that site shows your address was sent the coins then there's some sort of problem with your electrum wallet.
https://blockchain.info/