At first i thought the transaction was stuck, but it's not. You have over 3900 confirmations, so your coins are really therein that address,don't worry
You're probably using a bad Wallet, or you are wrong about the privatekey.
I don't know BCD very much. But I would try
https://www.electrumdiamond.org/ Electrum has more control over private keys.
Are you sure you put your private key, not your public key or something different?
Go to iancoleman.io , download it, insert your seed and look for the privatekey for the corresponding public address , just to be sure.
found an actual github repo that was for the real BCD diamond, loaded that shit up and I was able to send out a transaction. You the GOAT, send me your address and I'll send the bounty <3