Can't access wordpress site after changing domain

Hi,

My one-click Wordpress droplet worked just fine until I changed the domain name :

I built my website using just the IPV4 for a while, then I bought a domain name from Namecheap and followed the instructions Custom DNS on Namecheap + (A,A,NS) on DigitalOcean. I read that it took time for it to work so I waited 24 hours. The next day I go to my wordpress > settings > general and change the url to to the new domain name I bought.

Now I get “This page isn’t working [url] is currently unable to handle this request.” in both my domain name and the droplet’s IPV4.

I tried to edit wp-config.php

define( 'WP_HOME', 'http://example.com' );
define( 'WP_SITEURL', 'http://example.com' );

but it didn’t work, either with my new namecheap domain and even with my IPV4.

I also read that I should change something in phpMyAdmin but I have no idea how to do that.

Please help me fix my problem, Thanks.