Couple things at play here:

1. In October Microsoft banned on-device mining in Store apps. This means Bitcoin Miner can only do cloud mining where GroupFabric runs the miners.
2. CloudMining has GroupFabric pay the power and infrastructure costs; these costs have to be supported by ads.
3. Ads require foreground focus.

We're working on a new version that doesn't require the Microsoft Store. This version will have an option for no ads in exchange for a % of what is mined. When running without ads, it will also work in the background.

Still it don't work in the background as soon I turn of the screen the program stopped working only when I run a other program it will continue with working.

The concept is really great, but even with permission to run in background on Windows the app stops every second. Please fix that.

I know that this version is limited by windows sandboxing, but it would be amazing if you make an app that runs completely in the background, when you minimise it, it can go to tray.
And make it so the app starts with windows and goes to tray and starts automatically mining.

THIS VERSION COULD BE PUBLISHED ON THIS SITE AND NOT THE WINDOWS STORE!
That is how you can avoid sandboxing!

This would need to have pop-up adverts, as this is how Groupfabric generate their money "The mining pool exists purely to make the app easier to use and takes no fees as the app is ad supported. ".
I still like the idea though of having it as a service, and would take the pop-ups as a trade off.