No Caller ID dialog may be caused by different reasons, which depend on your device and telecom operators. Please make sure that you have already set up Whoscall as your "Default phone app"(Android7,8,9) or "Default caller ID & spam app"(and above Android10).
Due to the built-in system optimizer of OPPO, Mi, and Huawei devices, these devices would occur with no Caller ID dialog problem. Therefore, if your device were mentioned above, please make sure to turn off the "Power saving mode", "Battery optimize", and ‘Restrict background data ’. Or, you can add Whoscall to the Allowlist of these functions to solve the problem.
If you still do not see any information for incoming calls after following the instruction, please report your problem via the app. We will be happy to help you with the problem. (Tap ≡ on the upper left corner -> "Help & Send Feedback" -> "Caller identification problem" -> Swipe to the bottom and tap "No solution found?" )