@Erik Arwinge An .xlsx file is a format the portal doesn’t recognize, and it will always render as shown in the attached snapshot. You should be able to view a simple csv file through the portal blade if its a simple test file.
I see that your file is corrupting downstream when importing into Power BI, can you provide more details? Does the same happen when you try to download the uploaded file, does anything change or corrupt? Please let me know.