Idle Connection Error in Phoenix Live view

Hello, please I need help with Idle connection error in phoenix liveview on heroku. I could not reproduce this locally.

This is the error log:

heroku/router: at=error code=H15 desc=“Idle connection” method=GET path="/live/websocket?_csrf_token=N38KAycSARQ0LhcfODIZOjpDBW4kCXIj_G3UjMjquya2kQXwhwb-UO_P&vsn=2.0.0" host=app.betafolio.co.uk request_id=4d1040a8-bb3a-431e-9b59-5afa6f5d9aa2 fwd=“IP_ADDRESS” dyno=web.1 connect=1ms service=57293ms status=503 bytes= protocol=https

Please i need your help on this.