Api.twitch.tv/helix/streams?first=10 returns 404 not found

Thanks! I removed/fixed the confusing stuff there.

I hadn’t specifically picked a library myself and just let apps script deal with that - hoping it should work on the second response once I could get the token from the first.

How would I troubleshoot a library issue myself?

I’ve looked at the documentation here and just tried two things:
manually adding the required scope to the appsscript.json
and manually including the OAuth2 for Apps Script library
(though as far as I can tell that’s for the other end of creating/authorising tokens - and both of these things are meant to be automated)

Neither of that changed the outcome.