Hey everyone, longtime lurker turned member here.
I'm having a bit of a common issue which I've tried to troubleshoot. In short, I get the familiar hang up at the splash screen for P3D v3.4 where the splash screen vanishes after scenery loading and simply hangs as a background process. This occurred shortly after installing some add-on scenery for a while, then removing it. I have narrowed down the issue to the scenery loading in particular. If I make a change to the scenery.cfg file (say, turning a bit of scenery off), P3D rebuilds the scenery and then launches without issue as normal. I get no issues for the duration of my flight, regardless of length. If I attempt to close P3D, then load it again without changing scenery.cfg, it hangs.
Here is a list of troubleshooting techniques I have already tried. I am aware that some of them are not directly related to the issue, but with a lack of error feedback I thought covering bases would help.
Delete the shaders folder, Prepar3d.cfg, and scenery.cfg from the appdata folders -> no change.
reinstall FSUIPC -> no change
reinstall all versions of simconnect -> no change
checked dll.xml for old addon entries/Carenado entries -> removed old entries, no change
updated FSDT's addon manager -> no change
checked scenery.cfg for non-existant, old, or redundant entries -> checked and removed, no change.
This scenery.cfg editing is a workable solution, but it's about the same as running on a leaky tire in my opinion. Any insight is appreciated. I'm hesitant to do a full reinstall as I am waiting for more of my addons to reach 4.0 compatibility.