Oauth Outage?

Hey ​@rdraths 

This may or may not fix your issue, however I do have suggestions on what you should check once on your end,

The token URL should be https://a.klaviyo.com/oauth/token, not https://www.klaviyo.com/oauth/token. Requests to the  www subdomain will fail or behave unpredictably. If you've been using that split setup that's circulated in the community (authorize on www, token on a), that's fine,,  but double-check the token endpoint specifically.
Also verify that your client credentials are still valid by checking your OAuth app settings. A  mismatch between client ID and secret,, or a recently rotated secret, can produce exactly this kind of inconsistent 500 at the token generation stage.

I also feel this could be account-level or app-level flag on Klaviyo's end. I would suggest creating a ticket with klaviyo support and include all three req IDs plus the timestamps. tagging ​@GabbyEsposito ​@Byrne C here as well, so that they can escalate this to right team. 

I hope this helps and thank you for sharing your question here in the community.

Cheers,

Arpit