Hi,
Thank you for the details, I have found the problem.
The site URL is using the “http://” protocolol in the settings explicitly, but the actual front-end is redirected to the SSL version “https://”. That causes the issue, because the plugin tries to request the WP_CONTENT_URL constant from WordPress, but it is using the non-secure protocol URL. When the stylesheet is enqueued, then it is not accepted by the browser, because it is coming from the non-secure protocol URL.
The best solution to this is to change the settings, so that the core site URL to the https:// version, it will avoid a lot of possible future conflicts.
I have made a tiny change to the core plugin files to force the correct protocol it resolved the problem, I will include that in the upcoming release too, it will ignore the protocol from the settings and detect automatically which one to use instead.