Identified - Due to an issue with an upstream provider, customers with .NET clients that perform OCSP certificate checking may be unable to connect. This issue will particularly affect users with .NET drivers versions between 1.8 and 2.6.1, inclusive. Affected customers will see connection errors with the following text: System.Security.Authentication.AuthenticationException: The remote certificate is invalid according to the validation procedure.

We suggest either upgrading to .NET driver 2.7 or higher, or add the following change to your application:

For .NET driver versions >=1.8 but < 2.0, the fix looks like this:
var connectionString = "mongodb://localhost"; // replace localhost with atlas cluster connection string
var settings = MongoClientSettings.FromUrl(new MongoUrl(connectionString));
settings.SslSettings = new SslSettings();
settings.SslSettings.CheckCertificateRevocation = false;
settings.SslSettings.EnabledSslProtocols = System.Security.Authentication.SslProtocols.Tls11 | System.Security.Authentication.SslProtocols.Tls12;
var client = new MongoClient(settings);

For .NET driver versions 2.0 through 2.6.1, the fix looks like this:
var settings = MongoClientSettings.FromConnectionString("mongodb://localhost"); //replace localhost with atlas cluster connection string
settings.SslSettings = new SslSettings();
settings.SslSettings.CheckCertificateRevocation = false;
var client = new MongoClient(settings);
Apr 30, 21:34 UTC

Identified - We have learned from Microsoft Azure's operations team that they are currently capacity constrained for M10 and M20 nodes in Europe West and UK South. They are adding additional capacity, however MongoDB Atlas customers may have delays and failures in cluster creation, in the addition of nodes, and in certain healing operations until this is resolved. Customers with urgent needs should consider a different cluster tier or region.
Apr 23, 16:38 UTC

Identified - We have identified an issue preventing cluster modification for some MongoDB Atlas clusters in AWS via the public API. API users will get HTTP 500 error codes. Users of the Terraform MongoDB Atlas provider will get similar errors. Users can use the web UI as a workaround.
Apr 22, 14:25 UTC