A 1014 error occurs when you are pointing your DNS record to another hostname in another Cloudflare account, by default this is restricted.
If you want this to be allowed, then the owners of the destination (in your case SquareSpace) need to allow this to happen, typically the way they do this is by creating a Custom Hostname for your domain on their zone you are pointing too - Custom hostnames · Cloudflare for Platforms docs
I would suggest reaching out to SquareSpace support here as they would be best placed to assist.