No one around here is the developer of the application you have mentioned. I have reached the app page and found out that Fast Image Viewer is developed by BitBank Software, Inc. You need to contact them or report this problem to Microsoft in case you feel you've been scammed with a non-working app. Microsoft threats very seriously these situations.
I recommend contacting the developers using the following email: [email protected]
If they don't respond or refuse to refund, report the application to Microsoft.
