Bad Request when sending message to Extension PubSub

[ – This is no longer valid – See post below]
Sorry for the delay. Nope… Still the same unfortunately. I’ve been reading other posts where you answer too and now I just want to clarify something.

1- Should I use the secret key provided by twitch under Extension Settings -> Secret Keys? Taking into consideration that I’m using external as a role in the payload.

2- If not and I need to create one, and I’m taking the risk in sounding very very noobish (lol), how do I make one? Do I need to pay attention to something in particular? Or a web like https://www.grc.com/passwords.htm would be enough to generate one and use it as a secret key?

3- What about the algorithm that I need to use? Does it matter?

Thanks!
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EDIT: I’ve changed the algorithm from HS512 to HS256 and now I’m just getting an empty response with a 204 CODE as the examples in the reference page shows, NOW it’s working right? Or it’s just a placebo haha