The mbtc is in the new wallet but I don't have access to this wallet or a least I cannot work out how to access it.
How did you figured it out if you don't have access to your wallet? Is the address on the link above yours or the funds were sent from your wallet to somewhere else? They should stay at the same address thile you are changing your wallet.
If the problem is in electrum then try to switch different servers. This usually helps me.