Hi,
Thanks for reaching out to the Microsoft Community and for sharing the details. I just want to clarify something first: when you try to create the contact list, are you picking contacts from the People (Contacts) folder, or are you using the names that pop up from AutoComplete in the email field?
This issue often happens when Outlook relies on AutoComplete suggestions instead of actual contacts, or when the list is being created in the wrong folder. To fix it, make sure your contacts are in the main Contacts folder and not in Suggested Contacts or another location. If they’re in a different folder, move them to Contacts.
When creating a contact group, try adding members from Outlook Contacts instead of the Address Book, and search by email address if names don’t resolve. You can also clear the AutoComplete cache under File > Options > Mail > Send Messages by clicking “Empty Auto-Complete List.
If none of these steps work, try creating the list in Outlook Web at outlook.com or your organization’s webmail. If it works there, the problem is likely with your local Outlook profile, and creating a new profile through Control Panel > Mail > Profiles should help.
Hope this helps! Let me know how it goes.
Kind regards,
Edward