"IDX20803: Unable to obtain configuration from" Error In .NET API On AWS

I have had a .NET API deployed on an AWS EC2 instance for a few years and about a month ago it started throwing exceptions on every request. The error does not occur when I run the server locally, only when running in my deployed AWS environment.

The original error message was: IDX20803: Unable to obtain configuration from: '[PII is hidden. For more details, see https://aka.ms/IdentityModel/PII.]'.

After testing with Microsoft.IdentityModel.Logging.IdentityModelEventSource.ShowPII = true;, the error message is: IDX20803: Unable to obtain configuration from: 'https://mydomain.us.auth0.com/.well-known/openid-configuration'.

Inside my service's AddJwtBearer I added:

options.BackchannelHttpHandler = new HttpClientHandler
{
    ServerCertificateCustomValidationCallback = (message, cert, chain, errors) => true
};

And now when I test my service in AWS the requests are no longer failing.

It seems that my service is having issues making an SSL connection to its OAuth configuration, but only when running in an AWS EC2 instance. In my browser I went to the configuration URL from the error message and it has a secure connection with a valid SSL certificate, so I'm not sure exactly why it would have an issue.

I found that many people had experienced issues related to a change in the Auth0 Certificate Authority (see this post), so I updated the version of Amazon Linux running on our EC2 instances and the issue was resolved.