HTTP 426 Upgrade Required means the server refuses to perform the request using the current protocol but will accept it after the client upgrades to a different protocol. The response includes an Upgrade header indicating the required protocol.
The server requires an encrypted connection and the client is using plain HTTP.
The endpoint only accepts WebSocket connections but received a standard HTTP request.
The response includes an Upgrade header specifying the required protocol.
Use HTTPS instead of HTTP, or initiate a WebSocket connection if that is what the server requires.