Issue with Acquiring Token for SharePoint using Azure App on Specific Tenant

Question

I'm using an Azure app and this code to obtain a token for SharePoint, but I'm encountering an error when I run the following code:

public async Task<string> GetS2SAccessToken(string authority, string resource, string clientId)

{

    string certificatePassword = configuration.GetSection("Certificate:Password").Value;



    byte[] certificateBytes = GetCertificateByteArray();

    var cert = new X509Certificate2(

        certificateBytes,

        certificatePassword,

        X509KeyStorageFlags.Exportable |

        X509KeyStorageFlags.MachineKeySet |

        X509KeyStorageFlags.PersistKeySet);



    var certificate = new ClientAssertionCertificate(clientId, cert);

    AuthenticationContext context = new AuthenticationContext(authority);

    AuthenticationResult authenticationResult = await context.AcquireTokenAsync(resource, certificate);

    return authenticationResult.AccessToken;

}

I get the following error:

vba
Internal.Cryptography.CryptoThrowHelper+WindowsCryptographicException: Keyset does not exist

   at Internal.NativeCrypto.CapiHelper.CreateProvHandle(CspParameters parameters, Boolean randomKeyContainer)

   at System.Security.Cryptography.RSACryptoServiceProvider.get_SafeProvHandle()

   at System.Security.Cryptography.RSACryptoServiceProvider.get_SafeKeyHandle()

   at System.Security.Cryptography.RSACryptoServiceProvider..ctor(Int32 keySize, CspParameters parameters, Boolean useDefaultKeySize)

   at System.Security.Cryptography.RSACryptoServiceProvider..ctor(CspParameters parameters)

   at Internal.Cryptography.Pal.CertificatePal.<>c.<GetRSAPrivateKey>b__67_0(CspParameters csp)

   at Internal.Cryptography.Pal.CertificatePal.GetPrivateKey[T](Func`2 createCsp, Func`2 createCng)

   at Internal.Cryptography.Pal.CertificatePal.GetRSAPrivateKey()

   at Internal.Cryptography.Pal.CertificateExtensionsCommon.GetPrivateKey[T](X509Certificate2 certificate, Predicate`1 matchesConstraints)

   at System.Security.Cryptography.X509Certificates.RSACertificateExtensions.GetRSAPrivateKey(X509Certificate2 certificate)

   at Microsoft.IdentityModel.Clients.ActiveDirectory.Internal.Platform.SigningHelper.SignWithCertificate(String message, X509Certificate2 certificate)

   at Microsoft.IdentityModel.Clients.ActiveDirectory.ClientAssertionCertificate.Sign(String message)

   at Microsoft.IdentityModel.Clients.ActiveDirectory.Internal.ClientCreds.JsonWebToken.Sign(IClientAssertionCertificate credential, Boolean sendX5c)

   at Microsoft.IdentityModel.Clients.ActiveDirectory.Internal.ClientCreds.ClientKey.AddToParameters(IDictionary`2 parameters)

   at Microsoft.IdentityModel.Clients.ActiveDirectory.Internal.DictionaryRequestParameters..ctor(String resource, ClientKey clientKey)

   at Microsoft.IdentityModel.Clients.ActiveDirectory.Internal.Flows.AcquireTokenHandlerBase.SendTokenRequestAsync()

   at Microsoft.IdentityModel.Clients.ActiveDirectory.Internal.Flows.AcquireTokenHandlerBase.CheckAndAcquireTokenUsingBrokerAsync()

   at Microsoft.IdentityModel.Clients.ActiveDirectory.Internal.Flows.AcquireTokenHandlerBase.RunAsync()

   at Microsoft.IdentityModel.Clients.ActiveDirectory.AuthenticationContext.AcquireTokenForClientCommonAsync(String resource, ClientKey clientKey)

   at Microsoft.IdentityModel.Clients.ActiveDirectory.AuthenticationContext.AcquireTokenAsync(String resource, IClientAssertionCertificate clientCertificate)

I'm only experiencing this issue on a specific tenant. Has anyone encountered this problem before or have any suggestions on how to resolve it?

Thanks in advance!