Im trying to upgrade a 22.1.46 robot solution to 22.1.48

When attempting to open the 22.1.46 .pegaProject file in the 22.1.48 studio a pop up appears stating "... the solution must be upgraded first .... do you wish to continue?"  If yes is clicked no further activity takes place

The 22.1 studio's all have 19.1 upgrade features where 19.1 solutions are easily upgraded so upgrading from 19.1 to 22.1.x is reasoably straightforward

Additonally in visual studio with the 19.1 plug in's upgrading solutions was simply a matter of opening an earlier 19.1 solution in the higher 19.1 visual studio environment 

However it is not clear how to upgrade between 22.1 solutions as stated above

Please advise