When transferring Omni-USDT to a BTC wallet, please use the main address to receive the money. If USDT is transferred to a child address, it will not show in your wallet. So please do not use child addresses to receive USDT.

If you have already deposited USDT into a child address, you can click "My Profile" - "Manage wallets" - 「+Add Wallet」in the below -"Import existing wallets" - "Private Key", then import the private key to generate a new BTC wallet to see the USDT received.