Can't scan double sided

I'm using Acrobat 2017.

When I try to create a pdf using my scanner, and scan "both sides," the option is accepted, yet it only scans the front sides from my Brother TWAIN scanner. 

Both sides scanning worked fine using this scanner in Acrobat 2015 on an older computer.

Is there a fix or workaround?  I need double sided scanning - that's why I bough a scanner that could do it!

Thanks!