My cell phone does not detect the camera or I cannot change
If the problem of not being able to switch cameras persists despite having performed all the above solutions, then it may be physical damage to the camera module. For example, if you get the “Camera Error” warning when you switch to the rear camera, maybe the module for that camera is faulty.
In another case, if when you open the camera application you see the image of the rear camera very well but you do not have the button to change cameras to turn to the front, then the fault may be in that camera.
Obviously in this case the solution is to have the device seen by a technical service. However, if you feel capable of disassembling the cell phone, maybe you can solve it yourself. If the problem is indeed a hardware problem, often the cause of the “Camera error” or the change camera button not appearing is due to the fact that the rear camera is not recognized, and it may be because the module of the same is loose, something that may have happened due to one or more drops of the equipment, which would not be strange.
As indicated in this video, the solution is simply to reconnect or readjust the connector of the camera module to the main electronic board to solve the problem.
Set the front or rear camera as “default”
Assuming the rear camera module is really bad (not just disconnected, as I stated above), then when opening the camera app you will surely see the camera error, which will prevent you from even switching to the front camera, which may be in good condition.
In this case the solution would be to start the camera application with the front one, but unfortunately most camera applications open with the rear camera by default, including the one that is pre-installed at the factory and third-party cameras such as Camera FV 5 Lite, Open Camera and Retrica.
Normally you cannot change the default camera that an application will use, but there are “selfie” apps that have the front camera set as the default. One of the ones I have seen still has this behavior is B612, which is available on the Play Store.