Update: I found the advice given in previous thread to open the Command Line and navigate to the directory Sequence Generator and type in "Sequence Generator"/recover. This I did and it did not make a difference, SGP 2.5.2.3 was unable to open, starting and them immediately closing without even showing the start-up screen. I have reverted to 2.5.2.1 again.
I had a W10 update on 1st October (but used 2.5.3.2 on the 3rd October) if that makes a differenence.
Barry