Instructions before uploading your track
No effects or plugins on the Master Bus. You should not have limiters, clippers, compressors or any anything else that could interfere with the mastering process.
The output should be around -6dB. If you are above this level do not turn down the master fader. You should select all channels simultaneously and push down the faders until the master is around -6.
The track should be exported a 24 bit WAV with 'No Dither' box ticked.
If you are unsure let us know and we will be happy to guide you through this.