Why can't I scan documents from a printer/scanner into a PDF anymore?

I used to use the Create PDF from Scanner function of Adobe all the time to scan hard copies of documents from my multi-function printer, which has a scanner bed and a document feeder, into PDFs that would appear on my desktop screen so that I could email them as attachments to people. Then I got a new computer, an upgrade from my older MacBook Pro, and this basic function no longer works. I don't know whether the problem is the printer or Adobe or some combination of the two.

Here is what happens: I put the document face down on the flatbed of the scanner, close it, then select (in Adobe) Create PDF from Scanner, like I always did. It opens a window that instructs me me to choose my device, which I do (a Brother DCP-L2540DW) and then the printer/scanner window appears, along with a message that the scanner is warming up (and my printer/scanner does indeed make warming-up type noises, which is encouraging). The window that allows me to select scanning options appears, and I select them (Flatbed source, 300 dpi, Black and White, US letter, etc) and click on the SCAN oval. And then NOTHING HAPPENS. I mean, literally NOTHING. And I've waited for up to five minutes for something to happen, and clicked on the SCAN oval again and again. My printer/scanner goes to sleep waiting for something to happen. I try to quit Adobe Acrobat so that I can re-open it and try it again, and I get an error message saying that I can't quit because I'm in the midst of a scan. What is going on? This used to be so simple, and now it's infuriating.

My new laptop runs on OS Sierra 10.12.6 and I have Adobe Acrobat Pro XI (version 11.0.22) installed.

Help??