This morning I noticed that the Power Apps web links changed and from within my Power Apps web part in SharePoint the app did not appear
Get the link for the app
When you click on the link your web part will appear as expected. However when you use this url in your SharePoint web parts you will find that your web part doesn’t appear.

Not appearing app
When you do use the above url. You will find yourself staring at the following web part:

Once you remove the TenantId=398… part of the url your web part will appear as expected.
I would expect this to be an issue that will be there only for a short period of time, hopefully this will help you get past this issue quickly.
Issue still there..
Is it linked with the recent powerapps integration in power bi ?
I am suspecting guest access