c# websocket-sharp can not connect socket .error "not Includes no Sec-WebSocket-Protocol header, or it has an invalid value"

Question

I am trying to connect (with windows form application) to a socket which use sec-websocket-protocol for authentication . in browser everything is OK but when i try to simulate that connection with c# it fails with error Includes no Sec-WebSocket-Protocol header, or it has an invalid value. . Log file :

20/11/2020 6:24:55 PM|Debug|WebSocket.sendHttpRequest:0|A request to the server:
                            GET /?encoding=text HTTP/1.1
                            User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:84.0) Gecko/20100101 Firefox/84.0
                            Host: ------.com
                            Upgrade: websocket
                            Connection: keep-alive, Upgrade
                            Sec-WebSocket-Key: M3Ce------tUGg==
                            Sec-WebSocket-Version: 13
                            Accept: * / *
                            Accept-Encoding: gzip, deflate, br
                            Accept-Language: el-GR,el;q=0.9,en;q=0.8
                            Cache-Control: no-cache
                            Origin: https://--------.com
                            Pragma: no-cache
                            Sec-WebSocket-Extensions: permessage-deflate
                            Sec-WebSocket-Protocol: 549b4ftghj423f4a26------------------
20/11/2020 6:24:55 PM|Debug|WebSocket.sendHttpRequest:0|A response to this request:
                            HTTP/1.1 101 Switching Protocols
                            Upgrade: websocket
                            Connection: Upgrade
                            Sec-WebSocket-Accept: J2344x5eH------
                            Sec-WebSocket-Protocol: 549b4ftghj423f4a26----------------
20/11/2020 6:24:55 PM|Fatal|WebSocket.connect:0|WebSocketSharp.WebSocketException: Includes no Sec-WebSocket-Protocol header, or it has an invalid value.
                               at WebSocketSharp.WebSocket.doHandshake()
                               at WebSocketSharp.WebSocket.connect()
20/11/2020 6:24:55 PM|Debug|WebSocket.closeHandshake:0|Was clean?: False
                              sent: False
                              received: False

Sec-WebSocket-Protocol value is a code that i get from another API .and i think i get the value correctly from the api . i checked that over times .

and this is my c# Code :

ws2 = new WebSocket("wss://" + "---------.com" + "/?encoding=text");

                ws2.Log.Level = LogLevel.Debug;
                ws2.SslConfiguration.EnabledSslProtocols = System.Security.Authentication.SslProtocols.Tls12;
                
                ws2.CustomHeaders = new Dictionary<string, string>
                    {
                            { "Accept", "*/*" },
                            { "Accept-Encoding", "gzip, deflate, br" },
                            { "Accept-Language", "el-GR,el;q=0.9,en;q=0.8" },
                            { "Cache-Control", "no-cache" },
                            { "Connection", "keep-alive, Upgrade" },
                            { "Origin", "https://---------.com" },
                            { "Pragma", "no-cache" },
                            { "Sec-WebSocket-Protocol", "549b4ftghj423f4a26------------------" },
                            { "User-Agent", "Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:84.0) Gecko/20100101 Firefox/84.0" }
                    };

                ws2.Origin = "https://---------.com" ;


                ws2.OnOpen += (sender, e) =>
                {
                    ConsoleWriteLine("OnOpen");
                };
                ws2.OnError += (sender, e) =>
                {
                    ConsoleWriteLine("OnError: " + e.Message);
                };
                ws2.OnClose += (sender, e) =>
                {
                    ConsoleWriteLine("OnClose");
                };
                ws2.OnMessage += (sender, e) =>
                    ConsoleWriteLine("Laputa says: " + e.Data);

                ws2.Connect();

is it possible Sec-WebSocket-Protocol value changes by seting wrong SslConfiguration . ( i am not sure that i should use System.Security.Authentication.SslProtocols.Tls12 ) ?

i tried :
1- deleting Sec-WebSocket-Protocol from header --> response error : HEADER_AUTH_WS or HEADER_WEB_SOCKET_SUB_PROTOCOL is empty
2- deleting line that sets SslConfiguration.EnabledSslProtocols --> nothing changed.