The Re-Sync Data button can be found under Company Settings (Integration tab) or at the top right of the page in the Inbox for Purchases and Sales (not available in the inbox for QuickBooks users). The Re-Sync button is primarily for re-syncing the data that AutoEntry pulls from your accounts package (supplier/vendor list, nominal accounts, tax codes etc). The sync button does not push any invoices or data through to your accounts package (it does not sync invoices for instance).
The primary use of the re-sync button is to sync up any changes that have been made by you in your accounts packages so that AutoEntry has the correct accounts and data to post invoices through to.
For example, if you have added new nominal accounts or changed tax/vat rates or tracking codes/cost centers etc, you need to re-sync the data so that AutoEntry has the full current list of accounts available to post to.
If any accounts or tax codes are missing from the drop down menus in AutoEntry, try re-syncing first to pull through the new data.
Re-Syncing the data between AutoEntry and your accounts package can take up to 5 minutes.
Re-Syncing data with QuickBooks Online is not required as the integration with QuickBooks will pull through new data automatically. It can take a few minutes for updated data to appear in AutoEntry so you can force the update using the re-sync button under the integrations tab.