After completing a part of a series of follower missions via the mobile app, the next of that series does not appear until you log out and back in, or switch contexts to BFA then back to Legion.
I.e. while doing the demon hunter class order hall’s second series of follower missions on Android (you must complete 4, iirc, missions in order), if you complete one you cannot see the next one in the series until you force the app to refresh available missions by either switching to BFA and back or closing the app completely and forcing it to log in again.
Expected behaviour: after completing a mission, the pool of available missions is refreshed, allowing you to complete a series of missions without using a workaround.