iPhone calendar not displaying events from subscribed calendars

My iPhone Apple Calendar app is not showing events from all subscribed calendars. My calendars are set to sync via iCloud, and in the calendar settings I have selected my Google calendar and Uni Outlook calendar to show but events from those calendars are not showing. I have a Mac and iPad Air 2020 and all events are showing on both of those calendars - it's just the iPhone Calendar app that is not working correctly. How do I fix this?