Important Changes following Version 3.21

In version 3.21, Litmos removed "public" Custom Settings from the managed package. These custom settings contained sensitive fields that could be accessed by certain profiles in your Salesforce Org (if those profiles were granted access to these Litmos Custom Settings).

https://help.salesforce.com/articleView?id=cs_accessing.htm&type=5

Moving forward, the Litmos Custom Settings will be "protected", which means the settings are no longer accessible to any profile type what-so-ever (including system administrators).

For customers upgrading to version 3.21, the "public" custom Settings will remain after your upgrade. Litmos recommends these Custom Settings are deleted in order to safeguard against potential security breaches.