Use of API in WordPress with SSL (HTTPS)

Hello, I purchased a WordPress theme that uses WU API to display the weather of a certain location. I registered for an API, checked analytics for errors - all good. My problem is that I upgraded my site to use an SSL and HTTPS, but the API calls return the HTTP version, resulting the website to be marked as Not secure due to mixed content ( HTTPS + HTTPS). Can you guide me on how to use your API with HTTPS? I checked and the API responses work on WU's end with HTTPS.