MacBook Air screen issue- any idea how to solve it? Have tried Cmd+opt+p+b but does not change it

The built-in Display Assembly is defective so you will need to get the laptop repaired. If Apple Stores or Apple Authorized Service Providers are not open in your region, then click on the "Contact Support" link at the top right of this page to see what options are available in your region. In some regions it may be possible to mail the laptop to Apple for repair.