answer from Copilot that may help you debugging the issue :

GitHub Pages provides a free automatic SSL certificate for your custom domain, but it requires that your DNS is properly configured. Here are some steps to troubleshoot:

1. Check DNS Configuration: Make sure your DNS records are correctly set up. For an apex domain like gaeilgoals.com, you should have A records pointing to the following IP addresses:

   185.199.108.153
   185.199.109.153
   185.199.110.153
   185.199.111.153
   

   If you're using www.gaeilgoals.com, you should have a CNAME record pointing to your GitHub Pages domain (username.github.io).

2. Wait for DNS Propagation: DNS changes can take up to 24-48 hours to propagate across the internet. If you've recently made changes, you might need to wait a bit longer.

3. Check GitHub Pages Settings: Go to your repository settings and scroll down to the GitHub Pages section. Make sure your custom domain is correctly set and try toggling the "Enforce HTTPS" option.

4. Remove External SSL Certificate: If you've uploaded an SSL certificate from another provider to your repository, remove it. GitHub Pages handles SSL certificates automatically and doesn't support external ones.

If you've checked all these and still have issues, it might be a good idea to contact GitHub Support for further assistance.