What happens if you restart your computer, then try to install MEP Modeler as the first thing you do? At that point ArchiCAD is definitely not running.
.................................................................................................... Get Archicad Tips at https://twitter.com/laszlonagy AMD Ryzen 1700X CPU, 48 GB RAM, Nvidia GTX 1060 6GB, 500 GB NVMe SSD 2x28" (2560x1440), WIN10 PRO ENG, AC20-AC26 Loving Archicad since 1995
