Picking up Plasmid DNA using Nanodrop, but not using Electrophoresis
Having a positive reading on the Nanodrop but no band on the gel can be due to a number of different issues (not exhaustive):


An incorrectly zeroed sample
Incomplete staining of the gel
Contamination of the sample
Human errors in loading of samples


You should try to exclude these possibilities by positive controls in order to find out the true reason behind the inconsistent results.