Before you contact support about this, we kindly ask you to go through this troubleshoot:
Have you made sure to use a computer instead of a mobile device or tablet?
Did you try using a different browser?
If none of these options work - here are the most likely reason you can't upload your file:
Wrong file format – Make sure that your audio file is in WAV or FLAC format.
The audio file is to big – The maximum file size you can upload is around 500MB.
Your internet connection – Make sure that your internet connection is stable and restart your internet connection.
Your browser – Please try another browser or update your current browser to the latest version and empty the cache.
Your firewall – Make sure that your firewall allows Record Union to upload files from your computer.