How can you access this bitaddress.com website?
The OP should probably be referring to
www.bitaddress.org They are open source indeed and have been one among the best source for generating Paper wallets in a secure offline environment.
Well, if the blockchain shows 0 zero balance it means you don't have a balance and maybe what you saw from bitaddress com is fake. If you sent a BTC on that wallet before and it shows zero on blockchain well, your Bitcoin is lost forever there is no way to retrieve them back. You might be scam by someone or you've been generated a fake wallet.
This might be due to OP checking up the bitcoin balance in other blockchains like BCH. Either way, there is no other go to check the wallet balance other than importing private keys in bitaddress.org and viewing them in a blockexplorer. So OP should have pasted his private key in bitaddress and verified the balance and would have posted the varied address alone in blockchain and could have verified it in other non-btc blockchains or addresses with 0 balance.