Thanks everyone for your comments and feedback, I feel confident that I can get this fixed with your help!
The website concerned is https://wortonkitchengarden.com/
Up to about six months ago I was using the Flexible setting on Cloudflare as the server used AutoSSL to generate an SSL with LetsEncrypt, but I ran into an issue where it stopped creating new certificates.
I followed this article https://bioinformaticsindia.com/how-to-install-cloudflare-ssl-certificate-on-cpanel/ on how to install a CF SSL on your server and all seemed fine until now.
There are origin certificates for:
*.wortonkitchengarden.com, wortonkitchengarden.com (2 hosts)
I wonder if the 524 has something to do with it being a Litespeed server. I’ll check-in with the hosts to see if they have any ideas on that one.
Thanks again, and if you have any more ideas any help is gratefully received.