Silent Background Printing Broken

For the last 2 years, we have used Adobe Reader DC, called from a third party application, to automatically print address labels to a Zebra label printer.  We would scan a barcode in the application and an address label would be generated and would then open in Adobe Reader and automatically print, without any further user intervention.

After the latest update, users now have to click Print on the Print dialog that opens.

Can anybody please advise how we can revert to the previous functionality?