[Purchased and installed Affinity Photo but it won't open]

 I just purchased Affinity Photo for my PC and it downloads and then won't let me run or open it. I've never had this issue with any other software I've purchased for this PC. 

 

 When I try to open it a message comes up that reads:

 

"Windows cannot access the specified device, path, or file. You may not have the appropriate permissions to access them."

 

I have tried disabling my antivirus and protection software. I've tried opening it straight from the downloads folder. Nothing works.

 

I own the PC and no one else uses it. I am the administrator. Do you have any idea why this message might be appearing and how I might resolve it? 

 

Otherwise I will need a refund as I really need some Photo software soon and I need it to work.

 

Many thanks.