Nice to meet you guys -- this looks like a great community 
OK here's the deal - I can't get certbot certonly --standalone to run. My answers to the critical questions are pasted below, but here's some getting started information:
I've got a permeant server running Windows 10 that I access via Microsoft Remote Desktop, and on which I have full admin rights.
That server runs Waitress to host a Python Dash app that serves to localhost on Port 3000.
I've installed Nginx on that server to reverse proxy the app using the following server block:
server {
listen 80;
listen [::]:80;
server_name fintech-test.co;
proxy_set_header Host $host;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
location / {
proxy_pass http://127.0.0.1:3000;
}
error_page 500 502 503 504 /50x.html;
location = /50x.html {
root html;
}
}
On the GoDaddy side, I've kept the default rules in the DNS and I've added an A Rule with the following parameters:
Type: A
Name: @
Data: 152.3.64.207
TTL: 1/2 Hour
My domain is: fintech-test.co
I ran this command: certbot certonly --standalone
It produced this output:
Saving debug log to C:\Certbot\log\letsencrypt.log
Please enter the domain name(s) you would like on your certificate (comma and/or
space separated) (Enter 'c' to cancel): fintech-test.co
Requesting a certificate for fintech-test.co
Certbot failed to authenticate some domains (authenticator: standalone). The Certificate Authority reported these problems:
Domain: fintech-test.co
Type: unauthorized
Detail: Invalid response from http://fintech-test.co/.well-known/acme-challenge/OX8ud7y_qOh2SASWzWsnqaxS8cODW_r-tJGzMfIDZY0 [34.102.136.180]: "<!doctype html><html lang=\"en\"><head><meta http-equiv=\"content-type\" content=\"text/html;charset=utf-8\"><meta name=\"viewport\" con"
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.
Ask for help or search for solutions at https://community.letsencrypt.org. See the logfile C:\Certbot\log\letsencrypt.log or re-run Certbot with -v for more details.
My web server is (include version): nginx 1.21.4 (mainline)
The operating system my web server runs on is (include version): Windows 10
My hosting provider, if applicable, is: GoDaddy
I can login to a root shell on my machine (yes or no, or I don't know): yes
I'm using a control panel to manage my site (no, or provide the name and version of the control panel): no
The version of my client is (e.g. output of certbot --version or certbot-auto --version if you're using Certbot): 1.21.0
Ideas for what might be fouling things up:
- I need to get into Windows Defender Firewall and add a rule or something to free Port 80.... but if that were true, then it seems like the webpage wouldn't serve, and right now, you do indeed get a splash page when you visit fintech-test.co.
- I need to configure something else within GoDaddy
- I need to adjust my server_name -- or other directive -- within my nginx.conf file
That's about all I got. Thanks for the help everyone 
