When I buy this theme one year ago, the preference “color & background” was free. Yesterday, I do a mistake and delete my background. When I try to get it back, the preference “color & background” was payable…why then I had this option for free ?
Looks like you’d activated the Custom Design trial mode at some point. In the Customizer’s Colors & Backgrounds panel, click “exit the preview” and you’ll be able to save your customizations instead of just previewing them.