inside the Bitcoin 2 data folder, after making a backup, you should put the wallet.dat that you backed up in there, then launch the wallet and make sure your wallet is on the same block as the block explorer at https://www.bitc2.org/block-explorer/ in order to know that it is fully synced. (Click tools to see the block number)

If that doesn't help:
Only when the wallet is fully shutdown, after backing up your current wallet.dat you can also try the oldest backup of a wallet that you have in the backups folder, by placing it in the same folder that has bitcoin2.conf and debug.log and renaming it to be wallet.dat. (That you backed up elsewhere, don't just overwrite it).