If you’re unable to find the Truecaller settings under Call Blocking & Identification, don’t worry, this happens once in a while.
This is an issue we’ve seen on certain versions of iOS and we’ve reported the same to Apple. In most cases, this issue fixes itself and starts working when you try again in a few hours.
If the issue persists for more than 1 day, please try the following:
Force quit iPhone Settings app
Restart your device
Quick guide on how to enable the settings for Call Blocking & Identification: