How to remove socket connection error Error during WebSocket handshake: Unexpected response code: 400?

Question

Node.js

Hello!
Gives this error when trying to connect via socket connection

socket.io-2.0.1.js:2 WebSocket connection to wss failed: Error during WebSocket handshake: Unexpected response code: 400

I have nginx and cloudflare
, google says that only enterprise has a websocket, I looked at all the tariffs there are websockets.
I disable proxying for a while, the error seems to disappear.
It happens that there is no error, that is, when proxying is turned off.
Who will tell you how to fix the problem?