When dealing with invoices in Novi, you may come across the error "Object reference not set to an instance of an object." This issue is centered on the QuickBooks Connection and is generally a timeout on the QuickBooks side. Think of when you are logged into a secure site for too long and they log you out after a couple of hours. 

When this happens, first check to see if QuickBooks is experiencing any technical difficulties or scheduled maintenance. The Intuit Developer Status page will show if there are any problems going on at the moment. 

If all is well with QuickBooks, next, refresh your QuickBooks connection to ensure that you are properly connected (this disconnects and reconnects). This only takes a few simple steps. Once your connection is refreshed, do a manual sync by clicking the "Sync Manually" button in the screenshot below, found on the Members screen. Visit the article in the link above for more information!