Thanks for your question though i did not find that website, i have advertised an ecommerce for sale in order to collect the money for charity, the customer approached me and after we negotiate the price, customer told me that all his funds are in that site and sent me screenshots to confirm that.
I was asked to register an account at GENERCRYPTO.com and customers sent the funds, once i tried to withdraw the funds, on every withdraw attempt a poupup pops up with firstly, deposit 0.005 btc in order to confirm external wallet (at Poloniex.com), then a second time ive tried to withdraw there is a popup of 0.01btc, membership activation. third time was another 0.015 for insurance, since they detected my ip came from Israel and they have decided that Israel is a risk country while insisting that israelis in a list of risk countries which is not true, and here i am stuck with about 4.8K worth of BTC in their wallet.
Fair enough. Your customer is a scammer himself, and he is the owner of that website. No one can withdraw a penny from this website. Basically, he traps people by saying all his funds are in this website and then transfers the balance to their account. Once the victim tries to withdraw the funds from this website, the website requires them to make a deposit, and people get scammed.
This is a known scam method. It is sad that you didn't know about it. I am sorry for your lose mate. I would suggest you try to recover the website that you supposed to sell. I don't know if you already transferred the ownership. If you did, check if you can recover your website. Never make a deposit on any website to be eligible to withdraw your funds.