How do I correct a "connection timed out" error during http-01 challenge propagation with Cert-Manager?

I’m following the How to Set Up an Nginx Ingress with Cert-Manager on DigitalOcean Kubernetes tutorial to try and set up HTTPS ingresses for my cluster.

I’ve got it working up until the end. However, the certificates never get issued. If I drill down from the Certificate, to the CertificateRequest, to the Order, to the Challenge, I eventually find this errorr:

Waiting for http-01 challenge propagation: failed to perform self check GET request 'http://cert-test.tanndev.com/.well-known/acme-challenge/kC9hDBr8qI89
8y1gqacU2BbytGBb21YfQHaCyUx1kEY': Get http://cert-test.tanndev.com/.well-known/acme-challenge/kC9hDBr8qI898y1gqacU2BbytGBb21YfQHaCyUx1kEY: dial tcp 165.227.252.80:80: c
onnect: connection timed out

Clearly, this is blocking the certificate from being issued. But I’m not sure what’s causing it because I can reach [that url](http://cert-test.tanndev.com/.well-known/acme-challenge/kC9hDBr8qI89 8y1gqacU2BbytGBb21YfQHaCyUx1kEY) just fine, via both a browser and CURL.

I’m not sure what else to even look for, so any suggestions would be greatly appreciated.

If it helps, the manifest for the cert-test app is here, and the manifest for the certificate issuer is here.

Thanks in advance!