ISPconfig panel works in https mode, so when trying to access via http, an error message is displayed.
Here is the message (I anonymized the domain name):
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">
<title>400 Bad Request</title>
<p>Your browser sent a request that this server could not understand.<br />
Reason: You're speaking plain HTTP to an SSL-enabled server port.<br />
Instead use the HTTPS scheme to access this URL, please.<br />
<blockquote>Hint: <a href="https://blabla.com:8080/"><b>https://blabla.com:8080/</b></a></blockquote></p>
The problem is that this message appears in plain text in the browser, it doesn't get interpreted as HTML by the browser.
What could be the cause of this behavior?