I have the same problem but a slightly better description for the problem. My devices that have been updated to iOS 17+ (now 17.3) cannot real time track older devices running iOS 16.5.7 and earlier. They can use the FindMe app to locate the device (but real time updates DO NOT occur). iCloud.com\find works but it will not not update after the initial display (no real time tracking also). But the device running iOS 16.5.7 (iPhone 8+ in my case) can track my iPhone 15+ (iOS 17+) just fine.
After iOS 17.3 still did not solve the problem, I decided to call apple support. After 45min with the first level tech support they escalated me to the next tier. Where we repeated several other things that had failed at the first tier (removing the app, turning family sharing on/off, changing iCloud settings. And several of these again turn the phone on/off. Finally to a complete reset and restore (which I resisted doing as I had 130gb of music on my phone and I feared I'd have to restore it manually w/iTunes; which I did have to do, and it took 4hrs after I got off the support call). So this senior tech wanted me to take the two phones and my Mac (don't know why) to the nearest Genius Bar (15miles away, a +30min drive, each way) so they could have a look. I was doubtful that a software problem like this could be fixed at the Genius Bar. I agreed to go. After showing and explaining the problem to the 'Genius', and giving him my case number; he took my iPhone 15+ w/iOS 17.3 to his supervisor. Within minutes they two returned and seemed to agree it was a software problem that they had both seen before. They consulted with another 'Genius' that had seen the same problem 'the other day' and the solution was to upgrade the old iPhone 8+ to a newer version that could run iOS 17. This would fix MY PROBLEM. I told them it would not fix the possibly millions of others that HAVE this same problem. I specifically asked if this feature was deprecated when iOS 17 was released. HERE THEY WERE VERY CAREFUL TO NOT SAY THAT IT WAS. But they said a newer phone would fix the problem.
WHAT!! I told them that the REAL problem would still exist, but I wouldn't care because I just wouldn't see it any more. I asked how many times a day they do they see this; they reluctantly said a couple of times a day, definitely several times a week. I asked if there was a fix? They suggested we do a full reset/restore of both phones and see if it corrects the problem. I asked have they ever seen that work in this specific circumstance - crickets; literally no positive response, other than it has fixed "other" problems. I explained that I'd reset mine, lost my music, and spent hours restoring. Was not going to go throught that hassle again... They went back to pushing a new phone. I asked why they thought Apple Support after having spent 90 minutes with me would send me to them for this problem, if they likely knew and had seen this before. LONG PAUSE. Sometimes we see something that they were not told. I asked if they read all my case notes, as suggesting another reset/restore didn't make any sense to do it again (obviously didn't read all of the notes). Another 2 hours wasted (one in store and 1 going to/from).
** Update **
I finally got through to Apple's Senior support, spent +2.5hrs with them replicating this problem (iOS 17.3 vs 16.x.x) and attempted various trouble shooting... I'm certain they are now aware of this specific problem. It is susposed to get elevated to engineering this week. I expect a call back next week. Let all hope that they can get this corrected in the next (17.4) release).
