@shakthi M , Thank you for reaching out. The reason this error is coming up is that you have not specified the correct reply URL in your Azure AD SAML Toolkit instance that you have registered in Azure AD.
The correct Reply URL is:
You have specified a wrong Reply URL which is:
Hence it's failing with that error. Please correct the Reply URL and do follow the steps mentioned in the following article: https://learn.microsoft.com/en-us/azure/active-directory/saas-apps/saml-toolkit-tutorial#:~:text=Adding%20Azure%20AD%20SAML%20Toolkit%20from%20the%20gallery,-To%20configure%20the&text=Navigate%20to%20Enterprise%20Applications%20and,and%20then%20add%20the%20app.
I have configured this same app from Azure AD App Gallery and have followed the steps mentioned in the article that I shared above and this app works flawlessly.
Hope this helps.
Do let us know if this helps and if there are any more queries around this, please do let us know so that we can help you further. Also, please do not forget to accept the response as Answer; if the above response helped in answering your query.