If you don't have the answer yet, I think 4 months is very long, I have been able to configure it after several weeks of trying everything, the truth is that the step of this issue is not clear.

The first thing is to know if you have everything in a docker. Anyway it should work if you are not in Docker.

The first thing is to configure the vhost of the server. For this case you must add to your vhost (depending on how you have it configured) for this case I am going to send configuration for ngixn: 

Edit the ngixn vhost and insert this:  

#odoo server
odoo upstream {
server 127.0.0.1:8069;
}
odoochat upstream {
server 127.0.0.1:8072;
}

map $http_upgrade $connection_upgrade {
default update;
'' near;
}

after your configuration:

server {
        listen *:80;
        listen [::]:80;
        listen *:443 ssl http2;

That's how I have it. insert this:

proxy_read_timeout 720s;
proxy_connect_timeout 720s;
proxy_send_timeout 720s;

At the end insert this:

location / {
proxy_set_header X-Forwarded-Host $host;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header X-Forwarded-Proto $scheme;
proxy_set_header X-Real-IP $remote_addr;
proxy_redirect off;
proxy_pass http://odoo;
}

location /websocket {
proxy_pass http://odoochat;
proxy_http_version 1.1;
proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection $connection_upgrade;
# proxy_set_header Upgrade "websocket";
# proxy_set_header Connection "Upgrade";
proxy_set_header X-Forwarded-Host $host;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header X-Forwarded-Proto $scheme;
proxy_set_header X-Real-IP $remote_addr;
proxy_redirect off;
}

gzip_types text/css text/less text/plain text/xml application/xml application/json application/javascript;
gzip on;

client_body_in_file_only clean;
client_body_buffer_size 32K;
client_max_body_size 500M;
sendfile on;
send_timeout 600s;
keepalive_timeout 300;
}

in the odoo.config configuration
you must add this:

limit_memory_hard = 2415919104
limit_memory_soft = 2013265920
limit_request = 8192
limit_time_cpu = 360
limit_real_time = 3600
limit_time_real_cron = 2
gevent_port=8072
http_port =
max_cron_threads = 1
workers = 3
websocket_keep_alive_timeout = 600
websocket_rate_limit_burst = 10
websocket_rate_limit_delay = 0.2
xmlrpc = True
xmlrpc_interface =
xmlrpc_port = 8069
xmlrpcs = True
xmlrpcs_interface =
xmlrpcs_port = 8071
proxy_mode = True

This works for me.