Welcome to Hubitat!
The Hubitat Mobile App is still pretty new. For some, it works very well. For others, issues like yours are not unheard of. My wife and I both use iPhone 7 phones, and have had very good success (although not 100% reliable.)
Previously, we both used the Hubitat built-in Life360 support for mobile presence. For me, Life360 was slightly more reliable.
Instead of trying IFTTT, I would recommend trying Life360.
If privacy is a concern, you could also try using Locative + Hubitat Maker API for presence. Locative has recently been updated in the iOS App Store (which is somewhat promising!)
