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It's online and it's working, here is the link :https://bittrex.com/Market/Index?MarketName=BTC-GBYTE

click on your wallet there, in find type Gbyte, next to the currency click on the green button.

I have reached there but this is the situation!

I see, the wallet is offline for some reason in bittrex, try other exchangers, yesterday it was working there.

Here are other exchangers : https://coinmarketcap.com/currencies/byteball/#markets