403 Forbidden for index.php on Nginx - php

Question

I am trying to configure a simple wordpress site in nginx on Ubuntu. I'm no linux expert, but I usually manage between following tutorials online and tweaking a few bits myself. I've also had this very site running on a previous server with nginx, which I configured myself. I've migrated to a new server but I'm setting things up slightly differently this time round, so starting from scratch.
I've got nginx, php, and mysql installed and configured. I know php is working as I have checked it with domain.com/php.info. However, when I try to access domain.com or domain.com/index.php I get 403 forbidden. If I point the server block to index.html, that is served correctly.
I have set folder permissions to 755 and files to 644, and the owner to www-data.
If I rename index.php to index2.php, I can access the page at domain.com/index2.php but if I then point the server block to index2.php, I still get error 403.
I thought my server block config must be wrong, so I used the generator at digitalocean but the result is the same. I've tried almost every suggestion I can find on google and nothing has worked. Config below, can anyone help? Thanks!
server {
listen 443 ssl http2;
listen [::]:443 ssl http2;
server_name www.example.com;
set $base /var/www/example.com;
root $base/;
# SSL
ssl_certificate /etc/letsencrypt/live/example.com/fullchain.pem;
ssl_certificate_key /etc/letsencrypt/live/example.com/privkey.pem;
# security
include nginxconfig.io/security.conf;
# logging
access_log /var/log/nginx/example.com.access.log;
error_log /var/log/nginx/example.com.error.log warn;
# index.php
index index.php;
# index.php fallback
location / {
try_files $uri $uri/ /index.php?$query_string;
#also tried the alternatives below
#try_files $uri /index.php;
#try_files $uri /index.php?$args;
}
# additional config
include nginxconfig.io/general.conf;
include nginxconfig.io/example.com.wordpress.conf;
# handle .php
location ~ \.php$ {
fastcgi_pass unix:/var/run/php/php8.1-fpm.sock;
include nginxconfig.io/php_fastcgi.conf;
}
}
# non-www, subdomains redirect
server {
listen 443 ssl http2;
listen [::]:443 ssl http2;
server_name .example.com;
# SSL
ssl_certificate /etc/letsencrypt/live/example.com/fullchain.pem;
ssl_certificate_key /etc/letsencrypt/live/example.com/privkey.pem;
return 301 https://www.example.com$request_uri;
}
# HTTP redirect
server {
listen 80;
listen [::]:80;
server_name .example.com;
return 301 https://www.example.com$request_uri;
}