Hi team
I had a problem with opening another app through my program, what I wrote is
Activitystarter.Action=android.intent.action.VIEW
Activitystarter.package=com.android.Arduino BlueControl
Activitystarter.class=appinventor.Arduino BlueControl.Screen2
Activitystarter.start activity
I hope you see my question and reply on it
See here Using the Activity Starter Component about how to find out the correct settings
It would really help if you provided a screenshot of your relevant blocks, so we can see what you are trying to do, and where the problem may be.
To get an image of your blocks, right click in the Blocks Editor and select "Download Blocks as Image". You might want to use an image editor to crop etc. if required. Then post it here in the community.
Taifun
Trying to push the limits! Snippets, Tutorials and Extensions from Pura Vida Apps by 
Taifun.
Thanks