iOS isn't updating the activity sensor (iphone_activity)

**iOS device model, version and app version**

**Model Name:** iPhone 12 Pro Max
**Software Version:** 16.4.1
**App version:** 2023.3 (2023.459)

**Home Assistant Core Version**
2023.4.6

**Describe the bug**
iOS isn't updating the iphone_activity sensor like it did in the past.

**To Reproduce**

- Historically, an update would be pushed to HA when this state changed. IE you get in the car and start driving, when iOS recognizes you're in a car the companion app would push `Automotive` to HA. Or when you're walking it would push `Walking`.
- After some time, around 11 minutes on a half dozen occasions, this changes to `Unknown` (_maybe a timeout?_)
- Opening the app in iOS pushes an update and HA correctly reflects the activity state.

**Expected behavior**
It should push the actual state as it did before without defaulting to `Unknown`. This is breaking some of my automations which check the activity of the device. I have _Periodic Update_ enabled but that doesn't appear to be fixing this.

**Screenshots**




**Additional context**