I have successfully integrated my Amazon Seller account with QuickBooks. However, I am unable to find the option to integrate additional marketplace accounts.

Hi there, @mbkcanadabiz. The reason you're having trouble connecting your eBay and Etsy accounts is that the old tool used to link them (OneSaas) is no longer supported by QuickBooks.
 

The Amazon integration was recently updated to work directly within the QuickBooks platform, which is why that connection was successful. QuickBooks is currently rebuilding the eBay and Etsy integrations to work the same way as Amazon.
 

For now, I recommend using a third-party app from the Integrations tab to act as a temporary bridge to sync your sales and expenses from eBay and Etsy into QuickBooks until the official updates are ready.
 

For more information about eBay and Etsy integration, refer to this resource: Understand changes to e-commerce app integrations.
 

If you have further questions or concerns, please let us know.