I have two application configured with FRONT CHANNEL LOGOUT but AzureB2C does not seem to be triggering Single Sign Out

Question

I have two applications configured in AzureB2C

• A Web Application (ASP.NET Web Forms application) - APP 1
• A SPA Application (Angular client side) - APP 2

For both applications I have enabled the front channel logout URL .

When I login into APP 1 and then open APP 2 in another browser tab I am automatically logged in to APP 2. This is exactly what I would expect i.e. Single Sign In

However when I logout of APP 1 . I can not see the HTTP GET request to the logout page for APP 2 being triggered and expected this to be triggered by AzureB2C to log me out of APP 2 . Hence I am still logged into APP 2 .

Why would the HTTP GET request to the logout URL for APP 2 not be triggered ?

I have followed the documentation and have configured the Front Channel logout URL for both and in both applications when the logout is user triggered I am passing the id_token_hint set to the id_token to allow azureb2c to verify the logout URL for each application.

Reference : https://learn.microsoft.com/en-gb/azure/active-directory-b2c/session-behavior?pivots=b2c-user-flow

Has anyone come across this issue ? Any help in understanding what I may have missed would be greatly appreciated.

Many Thanks