NGINX SSL Configuration Ignoring API Location Block - node.js

Question

I recently have been trying to use Let's Encrypts SSL service to upgrade my web application to https. My application is a React front-end that runs in the same AWS instance as an Express backend/api.
I've been unable to get the https version of the site working, as it makes requests to the non-SSL certified Express server effectively locking the https version of the site from using the backend.
My solution around this has been to try to configure an NGINX block to proxy the Node.js server. My NGINX configuration isn't complicated and looks like this:
server {
listen 443 ssl default_server;
server_name example.site.com;
root /home/ubuntu/react/build;
ssl_certificate /etc/letsencrypt/live/example.site.com/fullchain.pem; # managed by Certbot
ssl_certificate_key /etc/letsencrypt/live/example.sitecom/privkey.pem; # managed by Certbot
include /etc/letsencrypt/options-ssl-nginx.conf; # managed by Certbot
ssl_dhparam /etc/letsencrypt/ssl-dhparams.pem; # managed by Certbot
location /api/ {
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_redirect off;
proxy_pass http://localhost:3050/; //port where API runs
}
location / {
try_files $uri $uri/ /index.html;
add_header Cache-Control public;
expires 1d;
}
}
server {
listen 80 default_server;
listen [::]:80 default_server;
server_name example.site.com;
return 301 https://$host$request_uri;
}
This setup worked perfectly when I was running an http version, but seems to have completely broken down for https. NGINX seems to be completely ignoring the /api location block - whenever I try to directly navigate to an /api endpoint it redirects me to the location block below (the static file that serves the react application). I've fiddled around with all kinds of settings and can't for the life of me figure out why NGINX isn't taking the /api location block into account, or why the SSL certification would have changed how it moves through/reads the blocks.