Many thanks to all who made a suggestion and helped. I have been able to fix it. While waiting for your amazing responses, I decided to remove the certificate for the domain so that I can install a new one. I did that using:
sudo certbot certificates #List the current available certificates
sudo certbot delete --cert-name ample.ng #Remove the certificate
I also checked the configuration file "ample.nf.conf" and removed all SSL references..in fact, I created a new basic configuration file.
I checked NGINX to make sure everything was okay and then restarted the server after which I requested for a new certificate for the domain "ample.ng" and "www.ample.ng".
Many thanks again to the community and everyone who contributed.