On Android OS versions 11 and above, Truecaller needs to be set as the default Caller ID and spam app to identify calls and block spam, robocalls, and unwanted numbers.
Enable Caller ID and spam identification from Truecaller Settings
1. On your device, open the Truecaller app
2. Click on the profile icon in the top left corner > Settings > Calls
3. Click on Enable button in the Troubleshoot Caller ID section
4. Select Truecaller
Enable Caller ID and spam identification from device settings
1. On your device, navigate to Android Settings > Apps > Default apps
2. Select Caller ID and spam app
3. Select Truecaller