You said you had your webapp running on port 80 earlier. Were you able to connect to it using HTTP on port 80 from some device on the public internet?
You could stop Certbot and instead run your own app on port 80. Then if you can't connect to it from the public internet you know it's your networking problem. I am already convinced of that but it might help to be using your own app as you seek advice from networking specialists.
We are not a general purpose help site for networking problems. We often point out common reasons for those and educate about tools to help debug. We have already strayed well beyond that 