And if they claim today they added the network and tomorrow they remove the network then my millions would be lost that I intermittently transferred even I sent a test transfer beforehand? Laughable at best. What a sob story.
Sorry about your loss of $1,700
Public key/private key pair is the same for all networks. Coinbase has your USDT but they do not support the network that you used for USDT transfer and if Coinbase adds the network, they will credit your account
As others have said, it's always good to test with a small amount $10 or less, first
I do not know why it's common practice now to send crypto from 1 exchange to another, but many years ago, most exchanges had a warning not to withdraw to another exchange address or to any address that you do not control the private key to
I always install a wallet software for the cryptos that I buy and this gets me to study the crypto asset in more detail. If it's a crypto asset I cannot withdraw to a local wallet, I do not trade it