When we are attempting to use the new API: SocialService:GetEventRsvpStatusAsync as well as the prompt on mobile, the prompt is set with an offset that forces it off a mobile screen, making the feature unusable on mobile. This seems to be missing proper scale and aspect ratio.
Notice in the image that the prompt is offscreen and the buttons are unaccessible.
There was a bit of a delay getting this released on some devices but now the fix for this issue has been fully rolled out. Thanks again for your report.