HI @Anonymous,
Could you please share a screenshot of your flow's configuration?
Do you want to display the content of the excel file within the email notification?
According to the screenshot that you provided, I think the subject and the body of notification emails are both binary data. I have reproduced your issue on my side and the flow's configuration as below:
The flow works as below:
There is no way to analyze binary data in Microsoft Flow currently, so I afraid that there is no way to convert the binary data into readable text in Microsoft Flow. If you would like this feature to be added in Microsoft Flow, please submit an idea to Flow Ideas Forum:
https://powerusers.microsoft.com/t5/Flow-Ideas/idb-p/FlowIdeas
In addition, you could consider take a try to send an email notification with an excel file as the attachment file. I have made a test on my side and please take a try with the following workaround:
The flow works successfully as below:

Best regards,
Kris