Speculation at this point says the disconnect results when a machine performs a fast startup, setting the machine's IP address to 169.x.x.x. It's an old problem, but somehow it's come back in spades in the past two days. I have no idea what triggered the sudden outbreak, as there were no Win10 1607 patches issued on December 6, 7 or 8.
Microsoft acknowledged the problem Thursday, recommending customers try restarting their PCs (or performing a clean start). Woody writes that it looks like Microsoft's latest Windows 10 patch "didn't cause the bug. But the patch didn't fix it, either."