Good morning, @barbatrapid. 

Thanks for following up with us. 

As mentioned by my colleague above, any invoice that is brought over by Acculynx is solely how they bring that into QuickBooks Online. You'd need to reach out to their support to know the reasoning behind losing the Sales Rep on the invoice. Although QuickBooks Online integrates with third-party apps, the third-party app is who would be in control of the data that comes into QuickBooks. 

Please let me know if there's anything else that I could assist you with. I'll be happy to lend a helping hand. Take care