Sign up / Sign in failed
I cloned the source code 15 Dec 2021, use VS2019 to build on master branch and run. Without any code change, try to Sign up / Sign in, it reports:
Processing of the HTTP request resulted in an exception. Please see the HTTP response returned by the 'Response' property of this exception for details.

Same error when I tried to use my own B2C instance.
After set breakpoint to notification.Response.Redirect("/Home/Error?message=" + notification.Exception.Message);
the detail error message is:
Unable to get authorization code Could not load file or assembly 'Microsoft.Identity.Client, Version=4.37.0.0, Culture=neutral, PublicKeyToken=0a613f4dd989e8ae' or one of its dependencies. The located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040).
I issued pull request #119 to address this and to fix a problem that was occurring when your B2C policy names use mixed case and TasksController.AcquireTokenForScopes() calls were failing to silently acquire a token to access the sample API.
I had the same problem and adding "/tfp" to AadInstance parameter in web.config fixed it.
<add key="ida:AadInstance" value="https://parrotexamcom.b2clogin.com/tfp/{0}/{1}" />
I could login, however api call fails now.
Account always null, GetAccountAsync could not find any account in AcquireTokenForScopes method.
var account = await cca.GetAccountAsync(ClaimsPrincipal.Current.GetB2CMsalAccountIdentifier());
My user flows are named by using capital letters like B2C_1_SIGNUP_SIGNIN. Thanks to @Turbo549, by changing web.config values to lower case like b2c_1_signup_signin fixed the issue. Now the sample apps are working for me.
I can confirm that changing from B2C_1_SignupAndSignIn to b2c_1_signupandsignin in
<add key="ida:SignUpSignInPolicyId" value="b2c_1_signupandsignin" /> fixed the problem calling API. The whole sample works as expected.