It seems an update to MBAM (sometime in the last week or two) has effectively disabled both Network Discovery and File and Printer Sharing in Windows 10. That is, even with those features enabled they are non-functional.
I have two nearly identical PCs (both running Windows 10 Pro and both running Malwarebytes) on a home network that is shared with a NAS and various other devices. After years of trouble-free networking I discovered that when I open File Explorer on either machine I was suddenly unable to see any other devices on the network. After hours of failed troubleshooting I finally called Microsoft Tech Support and allowed them to connect to one of my PCs remotely. After a very frustrating hour they asked if I would disable my antivirus software so they could perform further testing. Within seconds of turning off Malwarebytes all my missing devices became visible in File Explorer! My other PCs, the NAS, the home theater - everything. And when I re-opened MBAM they all disappeared again.
Unfortunately, I can find no option in the Malwarebytes setup to account for this nor could I find any documentation here or elsewhere to explain what's happening which begs the question: Is this a bug?