Check and make sure that the device is connected to the internet and you are currently signed in on your account.
Check if the App is updated to the latest version. Otherwise, please follow these quick troubleshooting steps:
Log out of your account
Restart the device
Sign back in
Note: Programs like Hollow Trees & La Graviere are outdated programs and are either going to be deleted and replaced or updated. They were older programs before the App got developed, and they didn’t fully carry over.