Windows 10 and iTunes sync problem

Windows 10 Home, free upgrade from Windows 7 back in August. Fully updated. I don't use any extra antivirus, just the Windows Defender that comes with the system, and it is fully up to date. I tried everything with the firewall on and with it off. The default is 'on.'

An interesting thing happened this time I totally uninstalled and reinstalled. This may have been happening all along, and I don't know if it matters, but I'd never noticed it before. After the reinstall, I started iTunes without the phone plugged in. After a moment from startup, iTunes showed my phone as if it were plugged in, which I couldn't understand since it wasn't. I ejected the phone in iTunes, and that worked fine. Plugging the phone in works as it has (shows up in iTunes, able to navigate and listen to music/watch videos from it, just not able to sync.)

Didn't help. It installed the driver successfully, and the phone beeped as if it were just connected, but nothing changed in iTunes.

You really didn't change anything and it just suddenly worked? I have never used iCloud for anything, and couldn't even get it to work when I tried a day or two ago.

Correct. All parts are installed, all drivers are correct and functioning properly (according to Windows,) the phone shows up in iTunes (even says that it's running the most up to date version and will check again in a few days.) The Sync button is grayed out, I can't press it. I also can't manually back the phone up there; when I press that button, it goes gray for just a second then comes back, and nothing happens.

When you plug your phone in, does it still bring up the Windows prompt to import photos etc like it used to? Cause that doesn't happen for me either.

It lets me make those changes (adding a playlist, for example,) and I can hit apply. It looks like it does something for a split second, then nothing. The sync button never shows up.

At the suggestion of a friend, I looked up my laptop on the manufacturer's website, to maybe see if there are Widows 10 drivers that I might need to upgrade. Dell is not developing or testing Windows 10 drivers for my particular laptop (which is 6ish years old.) Any confidence that this is the root cause of my issue?

Nothin there helped either unfortunately.

If I don't say it again, I do want to thank you for your ideas, I really appreciate the help.

So I tried an experiment that gave me some hope, but not sure where to go next. I plugged my girlfriend's 4S into my computer (it had never been before.) Lo and behold, it did some of what I hoped it would: Windows brought up the small pop-up in the lower right corner (something like "What would you like to do with this iPhone? and the options of importing photos and videos, going to dropbox, etc) Her phone gave the "trust this computer?" prompt and the iTunes recognized her phone perfectly.

The Sync button was still grayed out, but all of the sync checkboxes (Automatically sync this iPhone when plugged in, Sync this iPhone over WiFi, Sync only checked songs and videos) were all unchecked, and the Sync checkboxes under the Music and Video (etc) settings were unchecked too, so that doesn't surprises me that the main Sync button was grayed out on the main page (iTunes wasn't telling it anything that it should be syncing, so it makes sense that you can't sync anything.) I didn't change any of them for fear of it actually working and erasing her music.

I ejected and unplugged her phone, and plugged it back in, but this time (and all others after) it didn't bring up the Windows prompt, so seemingly didn't work anymore (and my phone still didn't work.)

My thought is that her phone hadn't been associated with my iTunes before, so it had no problem working correctly that first time, whereas the times since it was associated, all all times with mine (which is obviously associated,) it screws it up somehow. What do you think?

Is there a way to disassociate my phone from my iTunes? That would at least give me the opportunity to try the same experiment.