Our live website is now down: unable to connect to the openid-conficuration endpoint. Called from .NET on IIS WebServer. Suddenly started failing at around 15:45.
'IDX10803: Unable to create to obtain configuration from: ‘https://mydomain.eu.auth0.com/.well-known/openid-configuration’
Inner detail:
“The request was aborted: Could not create SSL/TLS secure channel.”
Stating 2021-05-13, I got hte same issue. IDX 10803 UNable to create to obtain configuration from: (my domain)/.well-known/openid-configuration.
I had no code change. I bet something happened on Auth0’s end, being unable to serve the well knwon configuration.
If we do nothing and it magically goes away, that means someone at Auth0’s panic-fixed the whole thing.
My mistake - I missed the recent notifications about deprecation of TLS1 and 1.1
In .NET you can force your API to use TLS1.2 as follows:
System.Net.ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12;
That was one late night I didn’t need!! 
Perfect! Glad you have figured it out and thanks for sharing with the rest of community!
when did we get these notifications? this caused a lot of issue for us
I received an email on 19th Jan but I clearly didn’t realise the significance. I knew our WebServer supported TLS 1.2 and 1.3 and didn’t realise that .NET would insist on using TLS 1.0 if the later protocols were available.
Lesson learned…! 