Withdrawal blocked unless account is topped up

After server issues forced my account from MT5 to the web trader, I deposited another $1,200 to support the account. Following several trades, the balance reached $8,700 and I submitted a withdrawal request.

Only after requesting withdrawal was I told that I had to increase the account to $20,000 before I could take money out. I was also prevented from trading, so I need this restriction explained and my funds released.