Power BI has recently updated their APIs to enforce TLS 1.2, which might cause issues with publishing pbix files to Power BI.
If you are having issues with uploading pbix files to Power BI using Power Update, you can try enforcing TLS 1.2 on the computer where Power Update is running.
To enforce using the latest TLS protocol, you can update to the latest .NET framework
and download, unzip and run the attached .reg file.
Please review any legacy applications / services running on the computer that may need to use an older TLS version before applying the settings.