Error: Failed to start the transport 'WebSockets': Error: There was an error with the transport

Error: Failed to start the transport 'WebSockets': Error: There was an error with the transport

server {
listen 80;
server_name 52.xx.xxx.xx;

location / {
    proxy_set_header   X-Forwarded-For $remote_addr;
    proxy_set_header   Host $http_host;
    proxy_pass         "http://127.0.0.1:4200";
    proxy_http_version 1.1;
    proxy_set_header   Upgrade $http_upgrade;
    proxy_set_header   Connection "upgrade";
}

ubuntu server + nginx + .NET5
sudo nano /etc/nginx/sites-enabled/some-config.pl

Startup.cs

public void Configure(IApplicationBuilder app, IWebHostEnvironment env, IServiceProvider serviceProvider,
          IRecurringJobManager recurringJobManager)
      {
          app.UseForwardedHeaders(new ForwardedHeadersOptions
          {
              ForwardedHeaders = ForwardedHeaders.XForwardedFor | ForwardedHeaders.XForwardedProto
          });