Check Access Restrictions: Ensure that your web app has no access restrictions that could be blocking access to the Kudu site. You can check this under Networking --> Access Restrictions in the Azure portal.
Check Quotas: If your app exceeds certain quotas (CPU, bandwidth, memory), it can result in an HTTP 403 error, which could prevent access to Kudu.
Check App Status: Ensure that your app is running. If the app is stopped, you may not be able to access Kudu.
Try a Different Region: As you’ve noticed, sometimes creating a function app in a different region can resolve the issue. This could indicate a temporary issue with the Azure services in the original region.