Running iOS 12 b3 on iPad, created a shortcut which works just fine. Added a Siri trigger and this selects the right shortcut, displays 'running your shortcut' (correct icon appears) but then dispalys 'sorry, there was a problem running the app'.
I tried setting a Siri shortcut to view recent phots on iPhone and this worked (on iPhone and iPad)
Anyone managed a personal Siri shortcut that launches a Shortcut?