Using classic Outlook for Windows in business environments
I was having the same problem with contact details not showing in the right pane in the web version of Contacts/People, so I thought I would give the Windows Mail app a try to access my contacts
When I opened the Mail app in Windows, I got a message that the app needed to update itself, and after a short period, New Outlook opened, showing the same account that was in the Mail app previously, and clicking the People icon in the left column displayed my contact data in the same format I'm used to seeing in the web version of People
Appears Microsoft is trying to force users into New Outlook by any means possible