Signicat Express integration with Azure AD B2C

I am trying to use signicat express account to integrate as an openid identity provider in Azure AD B2C. In express account I have created client and used those details in azure AD B2C identity provider. Grant type used is auth_code. However, when I try to use it in my application, the request seems to reach signicat, however it ends up with error like below -

An error has occurred

Please try again, or contact support

Error code - invalid_request
Description - Invalid redirect_uri

Need some quick help in this regard.