In an effort to protect the Steem witness community account that was hacked immediately following hard fork 23.0, Steem witnesses launched soft fork 0.23.1. All top 20 witnesses have upgraded to this version which limits the @community321 account for transfers since the community no longer has control over the account.
Steem witnesses are working with Bittrex to resolve the issue and have funds returned safely.
Read the official witnesses statement here: https://steemit.com/witness-category/@softfork22888/steem-consensus-witness-statement-softfork-0-23-1
The Steemit Team