@lewis-rowlands
I believe that you are probably using LetsEncrypt certificates on your site (or or your hosting company is on your behalf). Their original Root CA cert expired yesterday which means that all browsers and devices need to be updated in order to trust their new Root CA. Since web browsers auto-update, most end users will not notice, but internet connected devices like our printers generally need to be manually updated.
I suspect that you are using a printer with HIX interface? (The mC-Print mosel is newer, and so has supported the new Root CA cert since very early firmware and is not likely to be affected).
If so, please update your HIX interface to to the latest 1.9.2 firmware version. You can do this via it’s built-in web interface.
Alternatively, if you are concerned about performing a firmware update, you can open the CloudPRNT settings page, find the “HTTPS trust level” option, and set it to “Accept all” save the setting and then your printer restarts it should be working again. This solution is less secure (in theory it means an attacker could spoof your web site, and the printer will not recognise the change) but quick and easy.