Exterior or interior? Your description is confusing. Pictures?

Exterior grade vinyl...like DuraDeck.

It is sloped and inspected. What kind of waterproof system would you suggest?

I have heard also that "duradeck" type material cannot stand up well to the heat in the desert and either the vinyl or the adhesives break down rapidly. If I'm mistaken, or received bad advice, so be it. Is there a company that supplies the vinyl material as a "kit" so I can install it myself?

My deck is exterior. I plan to install a patio awning to help protect from the sun, but won't completely cover the deck

Here's one. There are a few manufacturers and likely some local installers. I've used their finish coats as well as tile. Like a "flat" roof these require some care and expertise to install correctly.

https://www.westcoat.com/systems/alx/

thanks! I'll check it out.