It looks like it was in the past, as Cloudflare has assigned cass and logan to be authoritative for it on their end. Either it was accidentally changed or in the migration to Squarespace it happened, it looks like it was updated yesterday.
Eitherway, you’ll have to set the nameservers back at your Registrar, Squarespace, and then if that certificate issue persists it can be troubleshooted after.
If you want to use Cloudflare, you’ll have to set back the Cloudflare nameservers for your domain at your Registrar, Squarespace. There’s a guide linked above. You can find your nameservers in the Cloudflare dashboard at the bottom of DNS → Records (they appear to be cass.ns.cloudflare.com and logan.ns.cloudflare.com)
If you didn’t want to use Cloudflare anymore/you wanted to use Google DNS, you’d have to create the A/CNAME Records on their panel. Right now you’re using their DNS but with nothing created on your root domain or www.
Your domain is registered at Squarespace. Potentially because you used Google Registrar before and they shut down and moved everything to Squarespace.
If you did register it through Google Domains:
It looks like for now you’d still manage it through your Google Account and the Google Domains website, a bit confusing. See if you can’t find it there and set the nameservers back.