Hello, @lcgondellesm

I will recommend to examine the web server (Apache/Nginx) error_log in order to track down what exactly is causing the issue.

You can simply execute this command and then access phpMyAdmin in order to see the logged error message:

Apache on Ubuntu:

tail -f /var/log/apache2/error.log

Apache on On Centos:

tail -f /usr/local/apache/logs/error_log

Nginx on Ubuntu:

tail -f /var/log/nginx/error.log

Feel free to share any logged messages here so we can investigate this further.

Hope that this helps!
Regards,
Alex