I am having the same problem here.
The old (v5) api is working just fine, but the new api is giving me 429 errors, under all circumstances.
I am polling the top ~6k channels online every ~8 minutes, thus only making ~60 requests in single bursts nicely spaced out, but even after not running it at all on my personal network for hours I instantly get a 429 error, with a RateLimit-Reset of ~1 minute, a RateLimit-Limit of 120 and a RateLimit-Remaining of 0.
It was working fine for a couple days on my VPS, now it wont work on my vps, home network, or any IP, even with fresh & personal OAuth codes.
At least the old API is still working, but I would like to keep working on making the switch to the new one.