How do I get the songs to play in Soundcloud?

It would help if you indicate which smartphone you are using and which operating system it is running. In most cases, the remedy is simply to delete the app, shut your device down for a few minutes, then reboot and reinstall the app. Otherwise, you might find more information on the SoundCloud website.

Sounds like your phone doesn’t have the proper codecs to play whatever file format it is that soundcloud uses.