The existing version is Affinity Photo 1.4.1 which my husband installed on his macbook and seemed to work fine. I downloaded a trial from serif as I didn't know about the mac store (I used windows before, my husband died last year). I can no longer open it to see whether an update is available but there seems to have been a conflict between the two versions that I can't resolve. I read that the trials had been re-set but when I downloaded another trial I was told it had expired.
I don't know where my husband bought Affinity: I have a box for Lightroom with a serial number but nothing like that for Affinity and I can't open it to find out more....
My copy of photoshop and my pc are both obsolete which is why I wanted to look at Affinity. Sorry if I'm explaining it badly, I'm not very technical.