Big Blue Button installation error: "Challenge failed for domain", thereafter "500 Internal Server Error — nginx"


  • I wanted to install Big Blue Button on a Ubuntu virtual machine via SSH;
  • I followed correctly the official tutorial up to the "Install" section;
  • I entered the following command on the terminal: wget -qO- | bash -s -- -w -v focal-270 -s <here the domain name> -e <here the email> -g -k using real data on "here the domain name" and "here the email";
  • I got the instalation error detailed below;
  • Accessing the real "here the domain name" by HTTP gives me "500 Internal Server Error — nginx";
  • It is not accessible by HTTPS: "ERR_CONNECTION_REFUSED".

The installation error in its full glory:

A instalar certbot (0.40.0-1ubuntu0.1) ...
Created symlink /etc/systemd/system/ → /lib/systemd/system/certbot.timer.
A processar 'triggers' para man-db (2.9.1-1) ...
Saving debug log to /var/log/letsencrypt/letsencrypt.log
Plugins selected: Authenticator webroot, Installer None
Obtaining a new certificate
Performing the following challenges:
http-01 challenge for <here the domain name>
Using the webroot path /var/www/bigbluebutton-default/assets for all unmatched domains.
Waiting for verification...
Challenge failed for domain <here the domain name>
http-01 challenge for <here the domain name>
Cleaning up challenges
Some challenges have failed.

 - The following errors were reported by the server:

   Domain: <here the domain name>
   Type:   caa
   Detail: CAA record for <HERE THE MAIN DOMAIN NAME> prevents issuance
 - Your account credentials have been saved in your Certbot
   configuration directory at /etc/letsencrypt. You should make a
   secure backup of this folder now. This configuration directory will
   also contain certificates and private keys obtained by Certbot so
   making regular backups of this folder is ideal.
bbb-install: Let's Encrypt SSL request for <here the domain name> did not succeed - exiting

The Let’s Encrypt log in its full glory:


  1. since the problem appears to have started with the SSL certificate during installation, disabling/removing it could solve the "500 Internal Server Error"?
  2. if yes, how to do it without uninstalling and reinstalling Big Blue Button? (I suppose uninstalling and reinstalling would be more traumatic due to leaving residues behind to create brand new errors)
  3. if no, how to troubleshoot the "500 Internal Server Error", finding its cause and solution?

The problem of losing the connection to the server was pretty simple:

  1. The official tutorial tells to enable a Firewall (ufw) allowing only HTTP (port 80) and HTTPS (port 443) traffic;
  2. If I’m using SSH, I should have enabled port 22 too. Changing this allowed me to connect once again.

Now, about the "500 Internal Server Error" I’m getting through HTTP, the official troubleshooting page tells GreenLight is at fault, so reinstalling Big Blue Button without GreenLight "solves" it.

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