How do I find the error causing www not to work with my domain?

I set up my first server on a digital ocean droplet two months ago. The website operates great under ‘site.com’(this is not the actual address…). However, you can no longer access it with ‘www.site.com’. I set up certbot, and that worked at the time of set up, but it is having issues now, second to the DNS issue.

All of this goes to say, I can not figure out why it is failing to work with www, when it allowed me to use it last month.

I have an A Record for the domain itself, and then a CNAME with www as an alias of the domain. My assumption is that the server details may be incorrect. A related stack overflow thread suggested that you need a separate server detail in the same file set up with server_name as www.

Currently, this is what I have (The latter details of the server are left out after the server name):

server {
        listen 80;
        listen [::]:80;

        root /var/www/site.com/html;
        index index.html index.htm index.nginx-debian.html;

        server_name site.com www.site.com;

The location block and certbot info follows if that is applicable. This is how it is shown in the digital ocean docs that I read.

I tried checking the nginx logs, and the access logs work fine. The error log is clear of anything, so either it doesn’t work, or there are no errors.

Again, this is my first server/site, so I am open to any stupid and obvious mistakes that you can think of. I appreciate it!