Do I understand correctly that if I had this coin from mining, then my coins are lost?
Pretty much, if you have coins in a wallet there is no way to sync the wallet or even upload them to the only exchange that Musicoin is on. Devs pretty much scammed us all
There is a way to sync an old desktop wallet. I got my old V1.7 synced and it shows the amount of my mined coins. I missed the chance to swap the old coins to erc20-token. I read about a second chance to swap them will come?! Maybe i missed that again. As long as you can just transfer erc20-token to Dove-Wallet, a fully synced desktop wallet is still worthless.