I am having a similar issue, and Squarespace is blaming it on Let’s Encrypt and washing their hands of it. My url is www.christthelightoftheworld.org and the SSL certificate was active and working properly up until three days ago. All of a sudden, the site was no longer secure, and the only thing I can see is that the certificate name is issued for Squarespace and not my domain.
I’ve contacted Squarespace Support and they blamed the issue on Let’s Encrypt. They pointed me to the Let’s Encrypt status website and said you guys were having issues. They said it’s out of their hands and I just have to hope it’s fixed soon. Some strategy, huh? I’m beyond frustrated with SS, as I’m paying them to host a site that’s been down for three days now. Their answer was to make the site “insecure” again, but my site has already been indexed with the secured url. This is causing major problems because people are getting the scary “attackers are trying to steal your info” message when visiting.
Does anyone have any info on how to resolve this? I’m at a loss and Squarespace is zero help. I have a site that’s down and a certificate that is endlessly “processing”.