Hi , @lunalovegood
According to your screenshot , your tile name is the xxxx.pbix. I test it in my side , it works good , you need to check if your steps is right?
First you need to publish your report to Power Bi Service. And pin Visual as next, then save and refresh the PowerBI report, the Title can display well.And you can search this dashboard in your Power Apps.


And you can check the Tile Id and dashboard Id here:

In Power Apps ,this is the url to show the tile :

In addition, please check:
1)whether you have permission of the PowerBI content that you want to display in the tile
2)whether your system meet the requirements:
https://docs.microsoft.com/en-us/powerapps/maker/canvas-apps/limits-and-config
Best Regards,
Yueyun Zhang