External Azure SSO sign on issue

[Greg DeVries]

We are setting up a new Data Center Jira instance to which we will migrate from our existing Server setup once it is working. The issue I am having is that Single SignOn does not work externally.

I have an Azure Enterprise application that handles SSO and application proxy. SSO works fine internally, but when access externally, it goes through the Microsoft login, including MFA, but then get an error before getting to the dashboard:

AADSTS50011: The redirect URI '<<URL>>' specified in the request does not match the redirect URIs configured for the application '<<ID NUMBER>>'. Make sure the redirect URI sent in the request matches one added to your application in the Azure portal. Navigate to https://aka.ms/redirectUriMismatchError to learn more about how to fix this.

I have tried following the Microsoft redirect fix, but that does not solve the issue.

Any suggestions? I'm not sure why it works internally, but not externally.

Thank you.

[Greg DeVries]

When I add the redirect URI, I get to the Jira Dashboard login page. I then click on SSO and get this message: 

AADSTS501621: Regular expression replacement for claims transformation has timed out. This indicates a too complex regular expression may have been configured for this application. A retry of the request may succeed. Otherwise, please contact your admin to fix the configuration.

I am using a claim transformation to extract the first part of the email address for the UUI. Extract (user.userprincipalname) Could this be causing the issue?

Interestingly, I can press back on the browser and it goes to Jira signed in.