if you look fo the TX id you will be able to find if you send it to the right address. If you sent to the right address you need to see if you paid the Tx fee and if you paid it... well in that case probably the site to where you send the coins is a scam...
Either that or its wallet's out of sync and not showing the latest transactions. I have known block explorers to do that sometimes. If the OP has a transaction ID he should send it to their support and ask if they can see it in their backend wallet, and if they can't point them to a link to the transaction in a block explorer.