I have two wifi networks at home. One is trusted and the other is for Internet of Things devices. Sometimes my iPhone will connect to the IoT network meaning it loses its trusted status.
The fix was simple.
- Open Settings and press the ⓘ next to the IoT network option
- Disable
Auto Join
Now, it will only connect to the trusted network unless I force the change to the IoT network. I do sometimes need to do that for IoT device setup.