I also have the lifetime version but I decided not to ever go to version 9 as I don't like the constant "phone home" aspect. This is necessary for BD but I'm not doing any BD.
It is also to verify the registration every time you open version 9.
I veiw this as DVDFab calls me a thief until they verify I'm not.
The version 8 I'm using is from June this year.
It should still work with the older registration key AFAIK.
It has for me.
If this version 8 works for you with the old key . That might get you by for right now.
If it does that is what I would email to DVDFab . That you updated version 8 & your old key worked. That you no longer can find you email receipt . Ask if there is a way to verify your lifetime subscription with the old key.
BTW You should always save the receipt email if at all possible.