Discovered a new bug in Windows 10 that does not allow users to print: the PC does not recognize the printer. What's happening
New bug in Windows 10, but this time it's not the May Update's fault: it was there before, too, but Microsoft only noticed it now and communicated it via its online support site. The problem affects Windows 10 from version 1903 onwards and affects the printer when it is connected to the PC via USB port.
Practically, when a user connects the printer via the normal USB port and then turns off the computer and also the printer (or simply disconnects it), on the next reboot the USB port used by the printer disappears among those available for the device. So it remains usable for other devices, but the PC can no longer communicate with the printer as before. The problem, according to Microsoft, occurs only in specific cases due to a feature built into many printer drivers and can be circumvented with a simple fix. However, Microsoft is working to correct it and will release a patch in the future that will fix the problem. It is likely that this patch will be included among the July patches.
Windows 10: why USB printer doesn't work
If your USB printer driver contains a "Language Monitor", then you are likely to experience this problem. A Language Monitor is a .Dll file needed to manage some communication functions between PC and printer and to allow some software to read certain information about the printer. But apparently these .Dlls have problems that block the communication between PC and device, making the printer temporarily unusable.
Printer that doesn't work: how to fix it
Microsoft has confirmed, in the same page of its online support where it explains the problem, that the bug exists and that it is working to fix it. In the meantime, those who have this problem can easily get around it: just turn on the printer before Windows starts and not after.
The problem remains with the May Update 2020
Usersers should know, however, that this bug was only communicated by Microsoft on June 11 and, consequently, the patch has not been published yet. Those who are waiting to download and install the 2020 May Update, which has been available to everyone since June 10, will not find a solution to the problem in this first semi-annual 2020 update. At best, therefore, the bug will be fixed with an update included in the next "Patch Tuesday" that will be released on the second Tuesday of July.