Getting error after incorporating organisation setting


I have completed my organization setting. Community facilitator (CF) and Champions are my two hirarchy. Logic is Community facilitator should be able to access and view Champions data.

I have also user Custom user data to show the separate modules for CF and Champions after login.

Now After finishing my Oragnisation setting and level. we are getting below error.

The case sharing settings for your user are incorrect. This user must be in exactly one case sharing group. Please contact your supervisor.

Could you please let me know what could be the possible reason for it and how to resolve it ?