HitBTC app works via API. You need to set correct permissions for your API key to give the app the access you want.
Please check your API-keys rights here. Some functions such as withdrawals, transfers, display Balance, Order History, etc cannot work without your permission.
If you can't withdraw, check “Withdraw cryptocurrencies” box in API keys settings. If the box is already checked, contact us via this form.
See more: Withdrawals