First of all, the phone needs to find the chip. It may differ from phone to phone where the so-called NFC reader is located.
Place the phone on the passport and move it around until the dots in the "scanner chip" start. The phone should be completely still when they start until a tick appears.
At this step, the most common cause of error messages is that the phone has not been idle. It takes some time to scan the chip, so be patient.
Conversely, an error message can also be due to a "timeout" if it has taken too long to find or start reading the chip. The MitID app must be closed and restarted for all error messages, after which you can try again.
However, when using an Android phone, ensure there is not too much light. So move a little away from the window, for example.
Place your face in the frame, and keep the phone still before the "I am ready" button becomes active. This is especially important on Android phones.
Please hold the phone right in front of your face. There must be no angle between the phone and the face. Keep both phone and face as quiet as possible during the scan. Only move the phone back and forth when the app asks for it, not from side to side.
Keep your face and phone still as much as possible. If the face scan fails, try again with slow motions. For example, hold the phone with both hands. If necessary, try with another phone.
If you get repeated errors, it is probably because your passport image cannot match your face with sufficient probability. There may be several reasons for this, e.g. that the photo in the passport is not of sufficiently high quality or that you have changed your physical appearance since you took the passport photo.