Issue

In IE 11, embedded PowerApps application is not loaded properly, instead, I get the Sign-In screen.

Clicking the Sign_in will not load the app. Issue is sporadic.

Solution

We suggest clearing the browser cache and cookies for that specific SharePoint Site and Sign In again.

If the issue is frequent, please consider opening the page in another advanced browser (Google Chrome, Mozilla, etc.)

Related Articles 

• Adding Your First PowerApps Application to SharePoint
• Embed PowerApps on SharePoint On-Premises and SharePoint Online (cross-tenant)