it is impossible to say without having additional information. here are the steps you should take:
1. make sure your transaction is confirmed.
go to a block explorer like
https://blockchain.info/ and search for your transaction ID. now see if it is confirmed or not. if it is not, then your Electrum is telling you the same. read this about stuck transactions:
https://bitcointalk.org/index.php?topic=1802212.0 in short you can try something like
https://pool.viabtc.com/tools/txaccelerator/ to get it confirmed faster.
2. if it is not confirmed make sure your Electrum is connected to internet and it is done receiving.
click on that green circle. you should see this number (
https://blockchain.info/q/getblockcount) which is currently at 497,845. if you don't you have to select another server and let it sync. the issue should be fixed that way.