Let's Encrypt has stopped working

I have been using DuckDNS and Let’s Encrypt for a couple years now with no issues. I have put in a new network and I’m now using all Ubiquiti gear. I have set up a port forwarding rule for 443>8123 to the HA server. However, I’m getting errors connecting, and I see the following in my Let’s Encrypt log file. I have changed the personally identifiable info in the log below.

Requesting a certificate for mydomain.duckdns.org
Certbot failed to authenticate some domains (authenticator: standalone). The Certificate Authority reported these problems:
Domain: mydomain.duckdns.org
Type: connection
Detail: redacted IP: Fetching http://mydomain.duckdns.org/.well-known/acme-challenge/i1tI58YrIrcneHPe0cIStZvlCBl--sS2YLn7HV14M88: Timeout during connect (likely firewall problem)
Hint: The Certificate Authority failed to download the challenge files from the temporary standalone webserver started by Certbot on port 80. Ensure that the listed domains point to this machine and that it can accept inbound connections from the internet.
Some challenges have failed.

Any assistance trying to figure this out would be appreciated. I have gone through several tutorials and checked everything I can find but I’m not finding what the problem is. The “hint” says that the certificate authority failed to download the challenge files. Do I need a separate port forward for that?

Thank you for your time and assistance.

If you http challenges for let’s encrypt, then port 80 needs to be open and forwarded too.

Thank you for that! That seems to have fixed my error for Let’s Encrypt, and it successfully received the certificate. It appears that everything is working on my local and mobile app now. Your assistance is greatly appreciated!