It depends on the platform from which the caller is calling you. If the caller is an Android user, the Caller ID works regardless of what app is used to initiate the call. However, if the caller is an iPhone user, you won’t get a Caller ID due to platform restrictions.
Further, for a user calling you from Android, they should have a 3G, 4G, or a strong WiFi connection and the latest Truecaller version.