Fixed Sidebar Widget in Sparkling not working

I’m trying to fix the sidebar widget using a plugin called Fixed Widget Area. The form I’m displaying in the sidebar gets fixed, but the white background on the page doesn’t.

Take a look at the screenshots below!

Hello there,

I hope you are doing well today.

So, you want to ensure that the background covers the form in the sidebar?
Could you please provide a link to your website so that I can inspect it?

Best Regards,

I’m developing on localhost. Haven’t moved it to a domain yet. Is there any other way?

Hi there

Sorry but we cant assist without seeing your website, its necessary to debug a site with developer tools and without seeing it we cant do anything