UnderDogMiller
Well I can say that MS decided to kill windows builds of PHP (a month or so ago - maybe earlier) so everything with PHP is almost completely manual now in IIS. So if you aren't familiar with IIS and PHP inter-workings then you are pretty much at the mercy of guides online. Not as easy as it used to be with auto-installers, etc. With this being said people are seeing no choice but to switch to Linux as the PHP integration out of the box is simply superior now and much, much easier.
Your issue a very odd issue that I cannot replicate and I haven't seen elsewhere. Have you tried a completely different browser to see if your usual browser is caching something? Also, make sure the Callback Endpoint in the OAuth2 popup matches the Redirect URI in your App Registration.
Can you try var_dumping the URL in the Dispatcher to see what the actual URL the application is trying to match on so we can see why it's failing to match?
Cheers.
