I downloaded Orbx Central, checked the Scenery Configurator and most of the default scenery has a red triangle next to them. Now, when FSX SE is started, it loads the scenery up to 38% then stops. I start PREPAR3D v.5 and there's a message that says " there's a problem and needs to shut down." Since ORBX Central has been installed neither sims are working.

Have you tried settings run Force Migration.