You create a Power App portal. When a user signs into the portal the following error displays: user not found You confirm that the user's sign in…

To determine the cause of a sign-in error in a Power Apps portal, a key diagnostic step is to view the detailed server-side error information. By default, portals often show a generic, user-friendly error message. Disabling custom error messages in the Power Platform admin center for the specific portal will instead display the full stack trace and detailed error message on the screen. This information is crucial for a developer or administrator to diagnose the underlying problem, which could be related to the user's contact record, web role assignments, or identity provider configuration.

B. Create a custom error message.

Creating a custom error message is for improving user experience by displaying a friendly message, not for diagnosing the root cause of the technical issue.

C. Enable diagnostic tools in Lifecycle Services.

Lifecycle Services (LCS) is a management and collaboration portal for Dynamics 365 Finance and Operations applications, not for Power Apps portals.

D. Enable Maintenance mode.

Maintenance mode takes the entire portal offline for planned updates. It does not provide diagnostic information for a specific user's sign-in failure.

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1. Microsoft Learn. (2023). Troubleshoot Power Apps portals.

Reference: Under the section "Portal runtime issues

" the documentation explicitly lists "Disable custom errors" as a troubleshooting step. It states

"Disabling custom error messages will display the complete stack trace of any error that occurs when you browse to the page. This feature should only be used when you are developing or debugging the portal." This directly supports option A as a method to determine the cause of an error.

2. Microsoft Learn. (2023). View error logs for portals.

Reference: This document explains how to access error logs. It also mentions the alternative of displaying errors on the page: "To configure a custom error

see Display a custom error message." This implies that by not having a custom error (i.e.

disabling it)

the server error is shown

which aids in diagnosis.

3. Microsoft Learn. (2023). Lifecycle Services (LCS) for finance and operations apps customers.

Reference: The overview section clearly states

"Lifecycle Services (LCS) is a collaboration portal that provides an environment and a set of regularly updated services that can help you manage the application lifecycle of your finance and operations apps." This confirms that LCS is not the correct tool for Power Apps portals

making option C incorrect.