For the reinstall, the LMS365 APP you should do the next steps:
1. Go to your Course Catalog - Site Contents
2. Find LMS365 app click on 3 dots and choose Remove
(Confirm to return to Classic Sharepoint)
3. Choose LMS365 App and remove it
4. After you removed the App, please select 'add an app'
5. In the opened window choose LMS365 App and confirm installation by clicking on the 'Trust it' button
6. After you installed the app, please exit classic experience