Thanks,
What I did, removed ALL layers down to the original (pixel). Flood worked fine.
I added a new pixel layer and then flood selected the entire photo again.
So back to the original layer with the sky selected, I found no way to change the color.
In full discloser, i'm new to photo editing. So this is clearly my own lack of knowledge.
However, when testing the other product I was able to easily do what I wanted to do.
So far Affinity is NOT working for me and if i had to decide now - i would not buy it.
If someone has the patience to help me or point me in the right direction or just flat out tell me what I want to do can't be done, thats fine.
I also saw some videos on sky replacement, going to play around with those now.
Despite my negative tone, I do greatly appreciate all the help and quick responses.