mediumMultiple Choice
PL-900 Practice Question: Refer to the exhibit
Exhibit
{
"authentication": {
"provider": "Microsoft Entra ID",
"tenantId": "contoso.onmicrosoft.com",
"clientId": "12345678-1234-1234-1234-123456789abc",
"redirectUrl": "https://contoso.powerpages.microsoft.com/signin-aad"
}
}Refer to the exhibit. A Power Pages site is configured with the given authentication settings. When a user clicks 'Sign In', they are redirected to Microsoft Entra ID, but after successful login, they are redirected back to the site and see an error. What is the most likely cause?
⚠ Common exam trap
PL-900 often tests authentication configuration; candidates may focus on clientId or tenantId, but the redirect URI mismatch is a common cause of post-login errors.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The redirectUrl is not registered in the Microsoft Entra ID app.
The redirect URL must be registered in the Microsoft Entra ID app registration. If it is not, after successful authentication, Entra ID will not redirect back to the Power Pages site, causing an error. The clientId and tenantId are likely correct if the user is redirected to Entra ID and can sign in. HTTPS is required but the error occurs after login, so it's not the cause.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The clientId is invalid.
Why it's wrong here
An invalid clientId causes the redirect to Microsoft Entra ID itself to fail immediately, so the user would never reach a successful login page. It is tempting because a mismatched clientId is a common configuration error, but here authentication succeeded before the error appeared.
- ✗
The tenantId is incorrect.
Why it's wrong here
An incorrect tenantId prevents the redirect from reaching the correct Microsoft Entra ID tenant, so login would fail before succeeding. It is tempting because tenant misconfiguration is a frequent setup mistake, yet the stem confirms the user authenticated successfully before the error.
- ✓
The redirectUrl is not registered in the Microsoft Entra ID app.
Why this is correct
After successful authentication, Microsoft Entra ID only returns the user to a redirect URI registered on the app registration. An unregistered redirectUrl causes the post-login redirect to fail, producing the error the user sees on returning to the site.
- ✗
The site requires HTTPS but is using HTTP.
Why it's wrong here
An HTTP/HTTPS mismatch blocks the initial redirect to Microsoft Entra ID, since Power Pages requires HTTPS throughout, so login could not succeed. It is tempting because protocol misconfiguration is a genuine cause of authentication failures, but the stem shows the user reached and passed the login stage.
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Microsoft exam blueprint
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