ENVI 5.6 and IDL 8.8 are not compatible with MacOS 12 Monterey, but here’s a work-around 12.26.2021 Ben Castellani
Configuring a New Installation of IDL 8.7.3 or ENVI 5.5.3 on macOS 10.15 Catalina 29.33.2020 Anonym If you have recently upgraded from 10.14 Mojave or prior versions of macOS to 10.15 Catalina, and are running through a fresh install of IDL 8.7.3 or ENVI 5.5.3, please follow the steps detailed in this Help Article.