Answer calls while screen is locked

If you're unable to answer calls on your iPhone when the screen is locked and there's no pop-up for answering, you can try the following solutions:

1. Check Notification Settings as shown in the pic below
   1. 
2. Open the "Settings" app on your iPhone and go to "Phone." Make sure that the "Call Forwarding" and "Silence Unknown Callers" options are turned off. Sometimes, these settings can interfere with incoming calls.
3. If Do Not Disturb is enabled, incoming calls may be silenced or prevented from displaying on the lock screen. You can disable it by swiping up from the bottom of the screen to access the Control Center and tapping the crescent moon icon. Alternatively, go to "Settings" > "Do Not Disturb" and toggle off the feature.
4. Check your DND status - Settings > Do Not Disturb; Use Do Not Disturb on your iPhone, iPad, and iPod touch - Apple ...
   1. Check BedTime Status - Clock App; Use Bedtime to track your sleep on your iPhone - Apple Support
   2. Check your Sound Volume; Adjust the volume on iPhone - Apple Support
   3. Check your Ringer switch; If you hear no sound or distorted sound from your iPhone, iPad, or ...
   4. Check Call Audio Routing; Call Audio Routing Bluetooth / Speaker / Automatic
   5. Check Auto Answer Calls; Turn off Auto Answer Calls
   6. Check Connection with Bluetooth Audio; Stream audio from iPhone to your hearing devices - Apple Support
   7. Check whether in Headset Mode; If your iPhone is stuck in headphone mode - Apple Support
5. Sometimes, a simple restart can resolve temporary software glitches. Turn off your iPhone, wait for a few seconds, and then turn it back on.
   1. Restart the device. That's it.
   2. Still not solved --> Force restart iPhone - Apple Support
6. If the issue persists, you can try resetting all settings on your iPhone. This will not erase your data but will reset all personalized settings to their default values. Go to Settings > General > Transfer & Reset > Reset > Reset All Settings and confirm the action. Note that you will need to reconfigure your settings afterward. All settings—including network settings, the keyboard dictionary, the Home screen layout, location settings, privacy settings, and Apple Pay cards—are removed or reset to their defaults. No data or media are deleted.
   1. Reset All Settings: Return iPhone settings to their defaults - Apple Support:- Return iPhone settings to their defaults
   2. You can return settings to their defaults without erasing your content.
   3. If you want to save your settings, back up your iPhone before returning them to their defaults. For example, if you’re trying to solve a problem but returning settings to their defaults doesn’t help, you might want to restore your previous settings from a backup.
7. Make sure you have the latest updates installed.
   1. Update Over-the-Air (OTA) —> Update your iPhone or iPad - Apple Support (IN)
   2. Update using iTunes/Finder —> Update your iPhone, iPad, or iPod touch - Apple Support (IN)

If none of the above steps resolve the issue, it is recommended to reach out to Apple Support or visit an authorized service center for further assistance. They can provide specific guidance based on your device model and iOS version.