POST 403 error (AuthApiError) at /token endpoint


I’m using Angular to authenticate users but I’m having trouble with the ‘send authentication code + client secret’ part of the PKCE flow. In particular, I’m getting a 403 when I post to the /token endpoint using angular. Also, I’m not doing any posting myself, I’m using the following method provided in @okta/okta-angular

handleAuthentication(): Promise;

I can also see the okta-oauth-nonce and okta-oauth-state cookies in the dev tools but no tokens (obviously, the request failed).


Could this be due to bad headers?

EDIT: Included form data:

Another idea: this could be due to no Issuer when instantiating the OktaAuthService:

Thanks for looking.

Update: I can copy and paste the info in the failed post request into postman and get tokens successfully - truly confused why this would be: