ERR_CONNECTION_RESET after port forward on gateway

I have nginx running on port 7777.
I have this configuration:
server {
listen 7777 ssl;
listen [::]: 7777 ssl;

ssl_certificate /77/apps/nginx/conf/77.crt;
ssl_certificate_key /77/apps/nginx/conf/77.key;

proxy_set_header Host $ http_host;
proxy_set_header X-Real-IP $ remote_addr;
proxy_set_header X-Forwarded-For $ proxy_add_x_forwarded_for;

location / confirm / {
proxy_pass http: // localhost: 3100 / api / client / confirmContract /;
}
}

https://192.168.1.10:7777 works fine in the browser.

I made a redirect on the gateway from (outside IP) 8888 to 192.168.1.10:7777. I set the policy correctly.
In the browser, when entering the https://external.address.IP: 8888, the error ERR_CONNECTION_RESET appears.
The redirection on the gate is done correctly, I checked on another service that I ran on port 7777
Do i need to change something in the nginx configuration?