display verification code on my iMac desktop

I have a question: In the past, every time I logged on to a web site that had 2-step verification capabilities, that site would send me a 6 or 8 digit code to a device of my choosing (in this case, my iPhone12, iOS 16.0.3). That still happens. However, up until just recently, and at about the same time, I would also receive that same 6 or 8 digit code that would be sent to my iMessages and that same code would also be displayed on my 27” iMac desktop (Mac OS X Monterey 12.6) where I would or could simply click on the code to prove that I was who I said I was and I would be logged in. Except for the iPhone12 receiving the code, nothing else currently works. Now I know this is a convenience, but it is a good one. I have had this problem before and have contacted Apple chat. That nice young woman knew exactly what to do. Problem is, I didn’t take notes so I can’t duplicate her actions. Suggestions?