Unable to open some apps from iOS 12 Shortcuts
You could try using the "Open URL" action to open the app using URL schemes.

You can find some URL schemes by doing a Google search for it(here's a good list).

If you can't find it online, you can get it manually(you need a computer):


Download the .ipa of the app you want to get the URL schemes of(you can use iTunes)
Rename it from .ipa to .zip and extract it
Open the Payload folder
Right click on the application inside and chose "Show Package Contents"(or just open the .app folder if you're not on Mac)
Open the Info.plist file and look for "URL Schemes".