Please take a try to clear cache of your browser, and then try it again, check if the issue is solved.
If the issue still exists, please consider take a try to re-start your computer, then try your app again, check if the issue is solved.
In addition, please also check if you have provided proper account to sign in PowerApps on your side. You could consider take a try to run your app within PowerApps Mobile App within your Mobile device (e.g. Android device, iOS device, etc), then check if the issue still exists.
Community Support Team _ Kris Dai If this post helps, then please consider Accept it as the solution to help the other members find it more quickly.