Definitely, not an A.I. reply. We have been going nuts for the last 7 weeks with new cert and cert renewal issues. We were first told it was DNS configuration issue on the server, which it turned out it was not. We later found that the issue was possibly because we were blocking so many international countries from accessing our U.S. server. We went through country by country unblocking and testing until we found a country that was causing validation to fail. However, as you keep changing IP addresses/country of origins we are still having problems with new certs and renewals. Over the last 2 weeks we had over a hundred domains fail renewal. I disabled country code blocking on the firewall, tried running autoSSL but the certs were still not validating. That's when we started digging again and found that too many connections was likely getting a temporary ban on on CSF. Without knowing the IP addresses of the servers you are using we can't white list them.
We never had this problem until the aroundFebruary 15th which on Feb 18 there was blog post on your site stating the validation process has changed.
We are just going nuts on this.