If you get a warning about encrypted iTunes backup (ChatStorage.sqlite) you need to make sure to perform a brand-new iTunes backup by NOT ticking "Encrypt iPhone backup"  then extract ChatStorage.sqlite again.
Unencrypted iTunes backup

If the "Encrypt iPhone backup" flag is greyed out it means you have some sort of corporate account configured on your iPhone. If so, please delete all those accounts (like Exchange, VPN, etc).