Hi @Vaibhav Shah,
Thank you for bringing this issue to our attention. I was able to reproduce the problem and successfully update an existing web app using the "Update an existing web app" option. It's possible that the issue could be related to permissions, especially if the Azure Active Directory (AAD) configuration isn't fully synchronized or if the user account lacks the necessary permissions to update the app. I recommend double-checking that your AAD settings are correctly configured and that your account has the required roles (such as Contributor or Owner) on both the web app and the associated Azure resources.
I hope you understand! Thank you.