Tasks (jobs) only show up in the app for the users they are assigned to, so an engineer will not see jobs assigned to someone else. To get tasks to appear for a different engineer, a Manager or above can reassign the visit containing those jobs to them using the Reassign option on the web Visits page; this moves the visit and its pending jobs to the new assignee, making them visible in that engineer’s app.
If the engineer cannot see tasks that are assigned to them, check that the app has refreshed its visit list while online, since visits created elsewhere after the device went offline never arrive. Also verify that the offline cache is up to date by opening the Visits tab for that day while connected before losing signal, as the app caches only your own visits for yesterday, today, and tomorrow by default. Offline changes and new visits generated remotely require a sync to appear.