At least in my own experience, the online instructions for ProCamera to enable and shoot 48MB ProRaw images are incorrect.

Here is what finally worked for me:

In the settings:
Max capture quality MUST be either natural or high
M&SI quality  mode MUST be either highly detailed or natural – Quality setting cannot be either of the unprocessed options

On the main camera screen:

If you do not have this set as above, then you will not even see the “HDR” and “48M” buttons

and further, SI must NOT be highlighted to get 48mp. (If “SI” is highlighted in blue, you will get a 12MP image.)

Or at least, all the above was true for me. 

HTH