Unfortunately, you're the only one able to provide (yourselve) the required information. We, as volunteers of this Community, can only try to guide you. There isn't any public information regarding these matters.
I think you'll need to find out a few things:
- Which server is hosting the website
- Aquire root access to that server
- Find out which ACME client has been used in the past (most likely
certbot, but other clients could be used too)
- Depending on the ACME client used, trigger the renewal
By the way, I think you have bigger issues, as your site http://w.sloche.retail-url.com/ returns an empty page. And the HTTP page doesn't redirect to the HTTPS version of the site. Not that it would matter much, as the HTTPS version of your site is empty too.