New Outlook: I cannot add a new contact to People.

This article has some high level steps to run new Outlook and classic Outlook on the same machine, Run new Outlook and classic Outlook side-by-side - Microsoft Support.

The classic Outlook start executable Outlook.exe is in this folder, C:\Program Files\Microsoft Office\root\Office16. You can right click on Outlook.exe and click Pin to Start if it is not already there. Double click on Outlook.exe to run it and then right click on the icon on the Task Bar and click Pin to Task Bar.

If you try to start classic Outlook but it switches back to new Outlook you can set the registry key in this article to stop that from happening, Toggle out of the new Outlook for Windows preview - Microsoft Support.

I looked for help, but my Outlook doesn't have the toggle in the upper right to switch to the older (or new) version.

How can I go back to the old Outlook?

Thank you. I decided to go back to the old Outlook. I like it better.

I noticed today that the contacts in my test tenant switched from All Contacts to Your Contacts similar to what you have. My capability to add new contacts still works in OWA and New Outlook. I searched bugs and I see a bug was just escalated for this same issue for a customer tenant. In my opinion the best direction for you would be to escalate this to your Tenant Admin and ask to open a support case from the Admin Portal. Anyone else on this forum thread with an M365 account should do the same. I'll monitor the bug and share if any learnings or updates from it but in case it's something different please get a support case escalated through your tenant admin.