When I tested it on my mobile app:

• Directed Pickup works
• Call queue Pickup works
• Group call Pickup does not work - seems like it is not supported for mobile?

Thank you for making a test @Problem Solver!  One of our engineers also performed a test and discovered that currently, it functions exclusively on Android devices due to the availability of an HUD option for mobile. Unfortunately, iPhones do not support HUD at the moment. @Brad196810024 , we would greatly appreciate it if you could submit a feature request using https://ideas.ringcentral.com.

@Mary-Community_Moderator how comes HUD feature is now available on iPads, but still not iPhones? 

https://ideas.ringcentral.com/forums/958493-phone-messaging/suggestions/48508727-hud-on-iphone