I have the same problem. Coins appeared in my wallet and then disappeared. Support does not respond to emails. There are no answers on the telegram channel.
So sad for you, I didn't get any problem transferring my MB8coins from web wallet to my windows desktop app. I just followed their directions and read all the updates I received from them to my mailbox. Maybe you missed something that caused you the trouble. As far as I know, today is the closing of their web wallet.