I’m afraid I can’t help as I don’t use the HTTP binding, nor am I on openHAB3!
They only thing I can do is be annoying and point you to a massive thread. Be aware that this thread was started as a new binding for openHAB2, and then switched to openHAB3-only in early October - just in case you get confused at the mention of openHAB2 in there.
It’s usually this way round: 1 Thing, many Channels.