Add to Calendar test
Tap each option on your phone and compare what opens.
You seem to be inside an in-app browser (Messenger, Facebook, Instagram, etc.).
Calendar files often don't work here. Open this page in Safari or Chrome for a fair test.
1. https link to .ics expected: Add to Calendar
The iPhone fix. Should show the event preview with "Add to Calendar".
Add to Apple Calendar2. Google Calendar link expected: Add event
The Android fix. Opens Google Calendar's add-event screen (app or web).
Add to Google CalendarDiagnostics
Checking event.ics headers…