Ensure your device has been synced without any errors so that you have the latest jobs and information on your device.
If your job or task list is blank when you're expecting there to be jobs or tasks or if you're missing a job or task on that list, ensure that no filters have been applied to the list:
Generally, this issue arises when users have accidentally selected a filter such as 'On Hold' when there are no jobs they're assigned to on hold. This filter will remove all active jobs from being visible in the jobs list, changing this filter to 'Active' or 'Show All' solves this problem.
The field devices show jobs based on who is allocated as "Supervisor 1" on the job, similarly to above check the filter for supervisors and change it to "All Supervisors" rather than yourself or another supervisors name so that you have a list of all jobs you have access to on the field device.