USDT TRC20 Problems Sending From Ledger
Sending TRC20 USDT from a Ledger device usually goes through a companion app, and failures tend to happen at the handoff between the device, the app, and the TRON network.
Signing vs broadcasting
A transaction can be successfully signed on the Ledger device itself but still fail to reach the network if the companion app has a connectivity issue at the broadcast step — this looks like the transfer "didn't work" even though your keys and signature were never the problem.
Energy still applies
Using a hardware wallet doesn't change TRON's resource system — the TRON account controlled by your Ledger still needs enough Energy or TRX to cover a USDT transfer, exactly as with any other wallet.
Confirm independently
After sending, check the destination address on TronScan directly rather than relying solely on the companion app's confirmation screen, especially if the app showed any kind of connection warning during the process.