Same here. Some time ago transactions to send money to Binance didn't go through. Contacted them to ask why and the reply was Binance, crypto, unsafe, bla bla bla. Told them i knew what i was doing and after that they approved it. That was the only time i got questions.
Now using Coinbase to cash out mostly and sometimes Bitfavo, never had any problem with them (yet). Using ASN bank.
The first buy was probably a scam and now they are trying to milk you for more. This is 100% a scam.
Don't respond to DM's! Every DM is a scammer.
Have you tried a different derivation path?
Thought the reason we have ERC (Ethereum Classic) was because a sort of a hack? Don't know the details, so might be wrong.
Only accept ethereum from the real ethereum network, I have seen scams were they pay testnet ethereum.
So always check on https://etherscan.io/ if the ethereum is received.
Look under the tab Internal Transactions. The ETH is received but probably not showing because it was send as a internal transaction. Balance should be updated though.
Thanks for the warning!