If you happen to be on the wrong change due to not updating your wallet in time, this will get you back on track.
Verify that you are indeed on the wrong chain by comparing your block height to the explorer.
Update your wallet to the latest by downloading it from GitHub (don't start the wallet yet).
Navigate to the NIX data directory (see the OS dependent steps below).
Create a backup of your wallet.dat (either located on the root of the data dir or in /wallets) to be on the safe side.
Delete the following from the data dir:
blocks (entire directory)
chainstate (entire directory)
Start the new wallet. Wait for the wallet to finish syncing and you're good to go!
Hit Windows Key + R.
%appdata% and hit Enter.
Click on the
The data dir is located in
In the Top Bar locate and click
Go -> Go to Folder .
~/Library/Application Support/nix/ and hit Enter.