There are three common things that can prevent projects from showing up on your mobile device:
1. The user is not attached to the project they are looking for. Go the the project on the web app and navigate to Project Admin>Members and make sure the user in question has a checkmark next to their name.
2. Not using the correct Sync method for retrieving changes made on the web including new projects and survey form changes. To get all projects onto your mobile device, you must perform a Sync All which can be found when you first log into the app in the 3-dot menu in the top right corner.
3. Spotty connectivity can prevent all projects from being delivered to mobile, as can navigating away from the app while the sync is occurring, or allowing the screen going black during a long sync. You can make it so that your screen stays on during the sync, and do not navigate to another app until the sync completes.
Pro Tip: The more projects you are attached the longer the Sync All will take. You might consider removing yourself from projects that you are no longer actively working on.