The data protection operation was unsuccessful

I'm trying to get the sample MVC application from Kentor AuthServices deployed to Azure and using Okta as the IDP. I've jumped a few hurdles but have stumbled on the CryptographicException "The data protection operation was unsuccessful". I'm unsure how to resolve it.

When this occurs the URL in the browser is https://mysite.azurewebsites.net/AuthServices/Acs

Any assistance is appreciated, thanks.

Below is the kentor section of my web.config. I don't have an identity server so removed all the federation config..

<kentor.authServices entityId="https://mysite.azurewebsites.net/AuthServices"
               returnUrl="https://mysite.azurewebsites.net/"
               authenticateRequestSigningBehavior="Never">
<identityProviders>
  <add entityId="http://www.okta.com/1111111"
       allowUnsolicitedAuthnResponse="true" binding="HttpRedirect" 
       metadataLocation="https://dev-11111.oktapreview.com/app/1111111/sso/saml/metadata"
       loadMetadata="true">
    <signingCertificate fileName="~/App_Data/okta.cert" />
  </add>
</identityProviders>

Let me know if I can provide any further info to assist you in assisting me!