I figured out a solution. FYI - There is a config.php file under config folder under web. I manually changed the totp from true to false and that did the trick. Now, the totp is not functional any more. Thanks a lot, @Th0m and Jesse. Your interaction helped me seek out different thought-process to address the issue.
@Th0m: If this discussion is within the scope of your background, I would appreciate your participation to address ISPConfig landing page issue. This login page was fully functional until yesterday, but started having issues after activating the ssl redirect option within the dashboard. Thanks. https://www.howtoforge.com/community/posts/406432/
Then you probably enabled an SSL redirect for a website that has no SSL enabled or no SSL cert. Redirecting to something that does not exist must result in a wrong page, most likely the apache default page or first website, being shown.
Thanks, @till. Yes, you are somewhat right. This site has been fully functional for some time now and the SSL certificate was also functional. However, by default, it was not getting redirected to the secure site automatically. For that reason, I enabled the redirect button under SSL tab for the mentioned domain to force the secure site as I have had done for other domains that are also part of this container system. Since then, I have been having issues. However, the two subdomains under this primary domain are fully functional including the subdomain discussed in this forum.
