Uploading file is stuck on 'Preparing for transcoding' – SoundCloud Help Center

You will see this error when our system is having trouble processing a track, causing it to be stuck as it waits to transcode.

Check the file format and length of your track. We support AIFF, WAVE (WAV), FLAC, ALAC, OGG, MP2, MP3, AAC, AMR, and WMA files. The maximum file size is 5GB. Tracks that are over 6 hours and 45 minutes long will not be able to be transcoded by our system.
Check our Status Blog to make sure that there are not any problems occurring around the transcoding process at this time.
Delete the pending track from your SoundCloud profile and re-upload it.