Blank landing page

Hi, I'm one of the managers of "domain.tld". Everything worked fine till about mid January. We then tried configuring the site with SSL certificates and resolving a problem we had with HTTP and HTTPS, because we wanted to redirect HTTPS to HTTP. A few days later we saw that the landing page now was just a blank white page. And when checking the Chrome console it seem like the website's first page wasn't properly loaded anymore. I can still access every part of the website by navigating via the URL, but the landing page is still blank. When I log into our Wordpress.org account, the blank white page issue is not happening and I can properly see the landing page. I did a backup restore from a date when I knew the site was working fine, but the blank first page issue is still there. Even after removing the generated SSL certificate that was added. I'm a frontend coder so I'm not very familiar with many of the server side and database related matters. Please let me what I can do to fix this. Thanks, Nils