Usually for one of five reasons: Tether froze the address, control of the address was handed to other keys, there isn't enough TRX for energy, the token isn't USDT but a fake with the same name, or the balance is shown on a site rather than on the blockchain. The check tests each one on the chain and says which is confirmed.

No. TRON has no mechanism where a payment to a third party lifts a freeze or opens a withdrawal. If a platform asks for a "tax", "insurance" or "verification" before you can withdraw, that is a sign of fraud. Don't pay.

Two common reasons. Each failed send attempt burns TRX on energy while the transfer doesn't go through. Or someone else holds a key to the address and takes top-ups within seconds. The check tells them apart from the address history.

It depends on the recipient: about 65 thousand energy to an address that already holds USDT, about 130 thousand to a new one. The check prices this in TRX at current network rates, counting your own energy.

No. The check reads only public blockchain data for the address. The test transfer is simulated without a signature and spends nothing.

Because not everything is visible on the chain. If the address isn't frozen, the keys are its own, the test transfer passes and there is enough TRX, the cause is off-chain: in the wallet app or with the platform. We say so plainly instead of guessing.