How to fix UE_5.5? won't create new c++ project/wont open editor

If your project isn’t creating a new project then I would suggest trying to change the engine’s build tool config. I was just able to build from source after changing it. Seeing as your project won’t compile / open I’d look there.

Go into your 5.5’s install folder then into \Engine\Saved\UnrealBuildTool
There you can add a custom config via a BuildConfiguration.xml file

<?xml version="1.0" encoding="utf-8" ?>
<Configuration xmlns="https://www.unrealengine.com/BuildConfiguration">
	<WindowsPlatform>
               <CompilerVersion>YOUR MSVC VERSION NUMBER HERE</CompilerVersion>
		<WindowsSdkVersion>YOUR WINDOWS SDK VERSION NUMBER HERE</WindowsSdkVersion>
	</WindowsPlatform>
</Configuration>

This will enforce the sdk & compiler version (ticks in the vs modify install don’t matter as unreal ignores them and looks most likely at registry keys)