Summary: Not all person views are listed while creating Groups
Symptoms: When we go to Groups and try to create a group respective of Person, All views or No view is not listed in the Source View dropdown.
Resolution: To resolve this issue, Follow the below steps
1. Take backup of your database
2. Run the below query:
update Custom_SysParams set parm_value = 'Y' where Parm_Name = 'AllowDupRecs'
3. Login to CRM
4. Refresh your metadata
5. Try to create new group