After the runtime Upgrade 1: State Snapshot migration (https://gov.centrifuge.io/t/runtime-upgrade-1-enabling-snapshot-state-migration/3000) the Altair-balance from the snapshot date can be found in the Polkadot app on the Altair-network.
If you don’t see your AIR-balance in the Polkadot wallet (https://polkadot.js.org/apps/#/explorer) you need to manually add your new Altair-account:
(1) Make sure the Polkadot extension is allowed and set to “Allow on any chain”. Change the network in the Polkadot app to “Kusama & Parachains” and “Altair”
(2) Because the Centrifuge-account and the Altair-account are connected you can add the AIR-account with the same seed phrase and json.file you used to backup your CFG-account. For adding your account with your seed phrase go to “Accounts”, click on “Add account” and paste your CFG-seed phrase into “mnemonic seed”. For importing it via the json.file click on “Restore JSON” and drag&drop the backup file. Enter the same password used for the CFG-account.
A friendly reminder: always store your seed phrase and json.backup file in a secure place!