How to enable javascript in Splash

I have been recently introduced to Splash. I'm currently trying to render the webpage of the company that I work at (I prefer not to name the company) in the splash API. When I try to render the page in the Splash API, the html contains a message saying:

"Our website can only be used properly with Javascript. 
 Enable Javascript in your browser."

At first I didn't understand where this error was coming from, until I disabled the Javascript in my browser and visited the site manually. Without Javascript enabled the same text that I found in the returned Splash html was now visible in my browser:

"Our website can only be used properly with Javascript. 
 Enable Javascript in your browser."

The weird part is that when I checked to see whether Javascript was enabled in splash by running the following script in the API:

function main(splash)
    assert(splash:go('https://www.whatismybrowser.com/is-javascript-enabled'))
    png=splash:png()
    return png
end

I got the following image:

It seems like Javascript is enabled just fine...

Question: Why is this website responding to my request as if I have Javascript disabled? How do I fix this problem? Should I add manual commands to enable Splash? (Sorry, I understand that it's annoying that I cannot provide information about the website that I'm trying to visit.)

Edit: To see the html in the website that I want to render I'm using the following script:

function main(splash, args)
   assert(splash:go(args.url))
   assert(splash:wait(15))
   return {
      html = splash:html(),
      png = splash:png(),
      har = splash:har(),
   }
   end