I’ve had a couple of Galaxy phones suddenly become very hit and miss on presence too. Google Home is looking like it may be more effective for my home location, which isn’t something I would have imagined being able to say given how utterly crap it used to be (completely random departures and arrivals delayed by minutes to hours).
The phones have recently had the February system updates but I didn’t take enough notice to be able to speculate on any correlation.
There is very little in the mobile app that couldn’t be done better elsewhere (be it a separate app or a website), so it’s particularly frustrating when one of the the few things it needs to be doing gets a bit ropey.
I am having geolocation issues too. My S24 Ultra geolocation routines all failed all of a sudden. I went through all of the steps in this thread. The pin on the map points to my house but the displayed address is about 2 miles away. Instead of doing the factory reset like Samsung suggested, I traded my S24 Ultra in for a S26 Ultra. The new phone has the exact same problem.
After support messed around I got up the next day and found my entire SmartThings including my V2 hub was gone! So, I had to start everything over from scratch. The address and geolocation were broken exactly like before.
Samsung support says they have escalated it. They want to see error messages? When an automated geolocation routine doesn’t run then there are no error messages.
When you got the new phone, did you perform a transfer of the ST app from old phone? Or perform a fresh install? There were cases in the past where transfer from one phone to another had issues with location. A fresh install of the ST app would usually resolve it.