Were you using Life360 previously and then it stopped working when ST shown groovy smartapps 2 weeks ago and now you are trying to enable the presence sensor through the ST app on the iPhone? Or were you using the presence sensor through the ST app and it stopped working and you never used Life360?
If you are trying to use presence through the ST app, go to Menu > Settings and enable “Get location for this iPhone” and ensure you have given it the proper permissions under iPhone > Settings > Smart’things.
Consider creating a virtual presence sensor for both iPhones so you can see the correct status for each in the ST app. You will need to create 2 Routines for each; one to set the virtual presence sensor to “Present” when your presence arrives Home and another to change the virtual presence to “Not Present” when the iPhone presence departs. below is the link to a good virtual presence sensor you can use:
[ST Edge] vEdge Creator: a virtual device generator for end users
Another possibility: if you have an Apple TV or one of the homePods at home:
How to Use a Meross Plug to Use HomeKit Presence to Trigger ST Routines
yet another possibility is to install an Edge driver that detects when you connect to your wifi network:
[ST Edge] LAN Device Monitor - #47 by TAustin
and finally there is IFTTT should the integration get fixed so at the time of this post, IFITT is not functional and they are working on restoring it.