First of all Happy New Year and many thanks for your replies.
No I am not.
Yes, the workflow was exactly as you described. This is really a bad surprise. As I thought that the problem was related to the product key that was not valid on my New laptop, I bought a new version of Affinity. OK, this was my mistake, however, I am badly suprised that when you purchase the Mac version of Affinity there is no warning or any remark that Affinity does not comply with Catalina!
Does anyone know whether there is a solution to be expected in the near future?