There are times a user might experience issues with their app such as data on the server / web but not on the device. Normally this is due to user security and a user not assigned to the team the data is in.
Here are a few things to try:
Confirm the user is in the correct team and has permissions to see data.
Is the data more than 2 weeks old? by default the app syncs back two week or 14 days . Try changing your sync settings to 30 days or more.
Try a hard reset of the app. Click on Profile and Settings, Logout & Reset App option.