Hi and welcome to the forum
Whe you say ‘stuck’ do you mean you have options to switch but it doesn’t work or you have no options to switch?
Have you replaced the old camera to see if that works?
If the old camera works you may have a faulty new one, else if neither now work it points to a connection failure in the cable|connector.
It’s a bit of a tight fit to get the connector off and back on the camera modules.
You may wnat to try again check for any debris that may have got to the connector.
By the way, when you get it to work it will still only show as a 12MPx output as the camera sensor is a 4 x 12MPs outputing 12MPx