Stuck on Let's Encrypt certificate issuance due to firewall issue even after opening necessary ports

Hello everyone,

I've been trying to set up a Mumble voice chat server on my home network using a Debian server. As part of the setup process, I need to obtain an SSL certificate from Let's Encrypt for secure HTTPS access to the server. However, I'm encountering an error when running the Certbot client to request the certificate.

Here's the command I'm running:

sudo certbot certonly -d mydomain.com

But I get the following error message:

Timeout during connect (likely firewall problem)

I've checked my firewall rules and confirmed that I've opened port 80 as required for the Let's Encrypt verification process. Here's the relevant rule in my ufw configuration:

80/tcp ALLOW Anywhere

Despite this, I'm still getting the timeout error. Has anyone else encountered this issue before? What steps should I take to troubleshoot further?

Thanks in advance for any advice!