What did you set as an addres when withdrawing?
You need to set your steem username in the address field.
Here is a guide to check for details: https://steemit.com/bittrex/@cryptos/how-to-transfer-steem-from-bittrex-to-steemit-com
The address you submitted is not valid for the STEEM network. Cancel this withdrawal and resubmit it.
What did you set as an addres when withdrawing?
You need to set your steem username in the address field.
Here is a guide to check for details: https://steemit.com/bittrex/@cryptos/how-to-transfer-steem-from-bittrex-to-steemit-com