# Oauth2 issuer certificate problem

Hi,
I’m using n8n on a windows server with node.
We installed our own oauth2 Server working fine with Postman and grant type client_credentials.
If I try to authorize an HTTP Reqeust with n8n using OAuth2 “Client Credentials” I get the following error.

Any Idea what the problem is? I tried to deactivate SSL verification without success.

Thanks
Eric

Hi Eric,

How are you running n8n? Normally disabling ssl verification while very risky should do the job I have seen reports of it not always working. I take it you are using a self signed certificate as well and not one signed by a CA / Lets Encrypt?

We are running n8n with node as windows service.
Yes the endpoint is using a certificate from our CA.
Unfortunately disabling the SSL verification did not help.

Thanks
Eric

Hey @Eric,

Is your CA an internal one or a “proper” one? If it is internal you might be able to grab the pem and set the environment option below it might do the job.

set NODE_EXTRA_CA_CERTS=c:\\path\\to\\cert.pem

I was looking for a variable like that. Thanks.

But, it seems like I need to disable HTTP2 support in IIS to get it running.

If i dont disable the HTTP2 support i get the following error.

Stream closed with error code NGHTTP2_HTTP_1_1_REQUIRED

Hey @Eric,

I never would have thought of that, So with HTTP2 disabled all is good?

yes, when HTTP2 is disabled in IIS everything works fine.
I also wonder since I though IIS would fall back to HTTP1 since i didn’t disable HTTP1.