Error
Warning: This item doesn't have a Cost of Goods sold account defined. You will not be able to purchase this item.
Cause
If you use Procurement in ConnectWise PSA, in the future you will not be able to batch over your purchases for this item. Those batches will fail because there's no COGS account. Since the integration doesn't have a GL account to put in the purchasing section, it creates the item without the purchasing section filled out. Without that section, QuickBooks won't allow that item to be selected to be used on a Bill or Purchase Order. i.e: you can't purchase it.
Note: this is a warning, not an error. Hence it won't prevent your batch from exporting.
Resolution
You can either deactivate the item in QuickBooks Online and re-batch, or you can manually add the COGS account in QuickBooks Online. To avoid this in the future, make sure you define a COGS account in your Revenue-Product GL mappings.