Your transaction has over 1500 confirmations, so it indeed definitely isn't a network/protocol related issue, but something at the operating side of hashflare. I doubt there's much you can do other then contacting their support, as they definitely received the BTC.

Also as a sidenote, i would really not advise you to buy these cloud mining contracts, as the companies behind them often disappear/it is usually a ponzi. Not saying that this is the case with hashflare, but there's a huge chance it is indeed a ponzi.