HTTP Error 500.30 - ANCM In-Process Start Failure error in ASP.NET Core 2.2

I've had the 500.30 error due to the duplicate identity problem cited by TanvirArjel, but I also just encountered the error when my appsettings.json file had some bad JSON in it. Not sure if that would only occur if you're actually trying to use configuration values in Startup.

I had this error come up. It turned out the root was because the app I was working with used Azure Key Vault, and I was using the wrong identity to authenticate with Azure.

I had to go to Tools > Options > Azure Service Authentication and change the identity used for Azure service authentication.

I got the reason. May be you are registering Identity twice in your application as follows:

One in ConfigureServices method of the startup class:

services.AddDefaultIdentity<IdentityUser>()
                .AddDefaultUI(UIFramework.Bootstrap4)
                .AddEntityFrameworkStores<ApplicationDbContext>();

And other in the IdentityHostingStartup :

services.AddDefaultIdentity<IdentityUser>(config =>
                {
                    config.SignIn.RequireConfirmedEmail = true;
                }).AddEntityFrameworkStores<ApplicationDbContext>();

Register Identity just in one place i.e either in ConfigureServices method or in IdentityHostingStartup.

Hope this will help you.