DSharpPlus Lavalink connection fails (server returned status code '404' when '101' was expected)

Question

I did create an Discord Music bot using DSharpPlus and made an Lavalink server for it. But when I try to connect to the Lavalink server I get this error in my Bot console:

[2024-01-14 21:30:38 +01:00] [401 /LavalinkConn] [Crit ] Failed to connect to Lavalink, retrying in 7500 ms.
System.Net.WebSockets.WebSocketException (0x80004005): The server returned status code '404' when status code '101' was expected.
   at System.Net.WebSockets.WebSocketHandle.ValidateResponse(HttpResponseMessage response, String secValue)
   at System.Net.WebSockets.WebSocketHandle.ConnectAsync(Uri uri, HttpMessageInvoker invoker, CancellationToken cancellationToken, ClientWebSocketOptions options)
   at System.Net.WebSockets.ClientWebSocket.ConnectAsyncCore(Uri uri, HttpMessageInvoker invoker, CancellationToken cancellationToken)
   at DSharpPlus.Net.WebSocket.WebSocketClient.ConnectAsync(Uri uri)
   at DSharpPlus.Lavalink.LavalinkNodeConnection.StartAsync()

I also get this in the Lavalink console:

2024-01-14T21:32:31.346+01:00  WARN 68551 --- [  XNIO-1 task-2] o.s.web.servlet.PageNotFound             : No mapping for GET /
2024-01-14T21:32:31.347+01:00  INFO 68551 --- [  XNIO-1 task-2] l.server.io.RequestLoggingFilter         : GET /

What does this error mean, and how do I fix it?

I allready did check if IP, Port, Passwort is correct, and tried rebuilding the Bot.