Hi,
Please try to go to your Order History or your Microsoft Store order history. Find the purchased app and check for details. Find the option for Request a refund.
If you do not have this option, it might be that it is not eligible for a refund. Please contact the Microsoft Store support regarding the purchase.
For Teams video, please make sure that your Teams App is updated.
May I know if the problem is playing video through Teams or if the camera is not working?
If it's the camera, try to take a camera test. Go to Settings > devices and click Test video to check if the camera works.
If the video was not working after the latest installation of an app, please try to disable or uninstall the app.
If you require further assistance, please don't hesitate to let me know.
Stay Safe!