I am also affected by this.   This feature used to work for US Quickbooks online and no longer has the ability to import estimates only invoices.   I did disable and re-enable the feature in QuickBooks labs which it started working, but only for a week.  Now it no longer works again. 

It DOES WORK for my Canada Quickbooks account so it has to be a bug in QB side. 

I have reported this several times to QB feedback, but no response yet.