Hi @michig,
Could you please share full screenshot of the flow you configured for your colleague?
I afraid that you created the flow with wrong trigger.
Do you want to create two flows, one is to upload files to SharePoint when new file created in OneDrive, and the other is to send email notifications when new files are created in SharePoint.
I have made a test on my side and the flow works well.
Image reference:


When I put a file to OneDrive folder(not test mode), the flow works successfully as below:


Please check that the connection you configured for your colleague is correct and that the file is placed in the correct folder.
Please let me know if the issue still exists.
Best Regards,
Barry