There are several different warning messages you may have received when you attempted to sync your invoices to Quickbooks:
SyncError in Intuit Data Services
This is an issue on Quickbooks Online's side, and is usually temporary. Please try again later, and if the issue persists, please contact us at email@example.com.
The name supplied already exists: Another product or service is already using this name. Please use a different name. Check your inactive Item List
This message suggests you are trying to create a product that already exists in QuickBooks. This may mean that you have duplicate products and services in Quickbooks. Please try using a different name for this item.
This error means that there was an issue in the connection between 17hats and Intuit. Intuit Data Services failed to respond to 17hats within a set time. This can result from Intuit experiencing an increased amount of traffic or issues with their servers. Unfortunately, there is nothing the 17hats team can do about this issue, so please be patient and try again at a later time.