Thank you very much! :)

Where exactly are you getting this error?

If it is in connection.start(), did you initialize the "connection" with "HubConnectionBuilder" and then finalized it with ".build()"?

const connection = new HubConnectionBuilder()

.withUrl('https://localhost:5001/hubs/chat')

.withAutomaticReconnect()

.build();

This way you create a connection with access to call "start()"