Could be something as simple as a dirty jack. Don't know which input you tried on the R-05 ("Line In", "Mic", or both), but my first suggestion would be to try cleaning the jacks with some DeoxIT D5 contact cleaner. Don't spray the stuff right in: put some on a plug, plug it into the jack a few times, twist it around, etc. If grime is the issue, it will clear it up pretty quickly.
If that's not the case, there could be a number of any other issues at play: bad connection, faulty component, some type of damage, etc. Good luck.