What are you using for a cable? The DP-01 has unbalanced 1/4" (6.3mm) inputs. (DP-01FX does have XLR's) The SM58 has an XLR connection. Wrong cable (not wired to transition from balanced XLR to unbalanced 1/4") may prevent signal from getting into the DP-01.
Does the DP-01 see signal from an electric guitar or other source?