....And BTC network is absolutely fine...
The mempool contains more than 180000 transactions at the moment:
https://blockchain.info/unconfirmed-transactionsTherefore the BTC network might not process transactions as fast as during
periods with less congestion. Maybe HitBTC has attached a too low fee and therefore
your transaction hasn´t confirmed yet? It is also possible that they batch transactions
in order to save fees and your withdrawal got broadcasted to the network at a later date than you think.