yes I am more confused with the system that bittrex apply and even for account creation just can not and for the verification process is also very difficult if like this constantly then the user inside will start to another exchanger and that moment of exchangers like binance or hitbtc to improve the quality as well as promotion again
Some exchange sites are disabled ADA deposit that means if there is a maintenance on the ADA itself or technical improvement. This is normal as long as the exchange sites are still running ada trade on their service.
Many people are having the same question as OP. Just be patient and waiting for the withdrawal to be enabled again.