My duo application stopped working

Cannot connect using duo ADFS Application anymore.

I get the error message in windows event logs:

DuoAdfsAdapter::BeginAuthentication called
User from claim: ‘DOMAIN\username’
Duo username: DOMAIN\username UseUpnUsername: False
Duo is unhealthy, invoking failmode.
Microsoft.IdentityServer.Web.Authentication.External.ExternalAuthenticationException: Duo is unavailable: Access Denied
Duo health check failed; failing closed per configuration

I tried creating another application to protect another application but still wont work.

My ADFS config was working fine until it just stopped, No changes made to ADFS or DUO.

Please help…

Hi @atGlitch, welcome to the Duo Community!
Have you tried testing your outbound connectivity first? If not, we have a Knowledge Base article that walks you through that process: How do I verify that I have TLS/SSL connectivity to Duo’s service?

If you have multiple servers, you’ll want to test connectivity on every ADFS server that has Duo installed on it.

If you try this and still run into problems, please feel free to contact Duo Support. We have a Community post on that process if you need extra help:
How to contact support and get help for Duo

Hope this helps!