For some reason I can't get the app to work on Pixel devices. The app worked great on my Samsung Note 8 & 9 but doesn't work on my wife's Pixel 2xl or my new Pixel 3xl.
No, it should work on any Android. Are you getting a blank screen? Try going to Settings -> Apps -> CalendarBudget -> Storage and click both buttons to clear cache and clear data. Then try the app again.