SAML Login behavior Custom Application

Hello,

I have a question regarding a custom SAML App that I have set up with AWS Identity Center as a SAML IdP.

I believe that I have set up everything correctly but when I login with AWS to get to my application, I get a 403 error. This caused me to believe that this was because of an incorrect configuration. But the puzzling thing is that when I get that error in the AWS Sign in page, I click the "Sign out" button and get redirected to the login page, and when I sign in again, I am not faced with the same error and can access my application.

The path which gives me a 403: Application url -> AWS login page -> enter credentials -> 403 error

The path which gets me through to the app, Application url -> AWS login page -> enter credentials -> 403 error -> click sign out -> AWS login page -> enter credentials -> App page successful

Any help would be appreciated as why this behavior occurs.

Thank you