I downloaded the latest QT wallet, replaced the wallet.dat but It does not seem to be working. Is the network working? I don’t see the blocks being updated. Should I restore in another way?
you need the client version that created the wallet.dat, network access is not required.
you then need to dump your keys and import them into a current wallet (and then send the funds to a new address generated by the new wallet).
Please check this guide: Blockmarket or Syscoin 2/3.x.x to Syscoin 4.x.x --- Upgrade Guide
just use the 4.2 wallet as target instead of what the guide says.