This could be due to your settings on both MyFitnessPal and your Fitness App. Please make sure the 2 following steps are done successfully:
- In your MFP account, make sure you set your profile to "public".
- Once the above is done, go back to your Fitness App. Within the "Connect Apps and Devices" setting, under the MyFitnessPal section, make sure you select the "Enable Share Diary" button.
For more details please also see How does a client connect MyFitnessPal to Trainerize?