Mixed SSL error when Hero Image feature is enabled

Hello vanilla forum. I'm having a problem with SSL in my site look at this screenshot:
While searching for the issue, I found this:
But I was unable to solve the issue and I still do not have any clue how to solve it. I have looked in to the plugin folder and plugin PHP files and I couldn't find a hint. Please help me to resolve this. I want the header image to be loaded in HTTPS rather than insecure HTTP connection.
Vanilla forum version : 3.3
URL : teamfoss.xyz
Area affected : All pages with Hero Image
Plugin used : Hero Image.
Thank you so much for helping. ❤️
0