Best answer by Aikasse
1. Sign in to https://soundcloud.com/ via desktop web browser using laptop (no smartphone)
2. Go to section:
settings > Account > Connected applications
... located at the following web page address:
3. Press "Revoke access" button in the line corresponded with "SoundCloud iOS/Android".
4. Uninstall & reinstall your smartphone Soundcloud app and try to sing in again.
I hope this may help to somebody!