Swipe down from the top-right corner to open Control Center (or swipe up from the bottom on older iPhones).
Tap the Focus icon (crescent moon) if shown.
Turn off Focus or select a mode that allows all apps/notifications.
Open Settings.
Tap Focus.
Select the active Focus mode.
Turn off options that hide notifications or hide app notifications.
Open Settings.
Tap Screen Time.
Tap Content & Privacy Restrictions.
Turn off Content & Privacy Restrictions.
Open Settings.
Tap Screen Time.
Tap App Limits.
Remove any limits for the app or turn off App Limits.
Open Settings.
Tap Screen Time.
Tap Communication Limits (if applicable) and adjust settings.
Check if the app was removed from the Home Screen:
Search for the app in the App Library.
Touch and hold the app icon.
Tap Add to Home Screen.
Check if the app is hidden in App Library:
Open App Library and use the search bar to find the app.
Touch and hold the app icon.
Tap Add to Home Screen.
Check if the app was deleted:
Open the App Store.
Search for the app.
Tap Get or download the app again.
Check if the app is restricted by age/content:
Open Settings.
Tap Screen Time.
Tap Content Restrictions.
Adjust iTunes & App Store Purchases / Allowed Apps settings.