[Document files won't open!!! Please help]

My document files that are saved using Affinity Designer will not open when I click on them from the desktop of my mac, or in a folder. I am able to open the program itself, but when clicking on a saved document when the program is open, this message appears saying that a retail version of the program is required in order to use the file....I already have a retail version purchased. Would I need to download a beta version of Affinity Designer too? Please help me with this issue. I don't understand why this is happening. 

[Affinity Designer Customer Beta (1.6.1 - Beta 5)]

I downloaded the beta link and it keeps telling me that in order to use it i must have affinity designer installed, but I already do. Is there a way to fix this problem so that I can use it to fix exporting issues?