WIndows 10 pc stopped recognizing an S9 phone cabled to the PC's USB port. The cable and port work fine with a Galaxy S8, and also worked (for file transfer) with this S9 phone a few weeks ago. When the phone is connected, the phone beeps and displays a notification about charging, but the pc does nothing. I have pored over many troubleshooting pages, but mostly they refer to menu choices that don't exist on my phone. With developer options and USB debugging turned on, the USB default options doesn't show "MTP" specifically, but does have "Transferring file / Android Auto" selected. Is there any way to diagnose or troubleshoot this problem?
On the menu, "MTP + ADB" is checked. Tried changing to "MTP", and it resets itself to "MTP + ADB" In either case, still no connection.