When you export images and georeference files using Nearmap's Export Imagery tool, Nearmap gives the files a name based on 5 components:

An example is:

EPSG28355_Date20150501_Lat-37.780075_Lon144.961513_Mpp0.597.jpg

EPSG28355_Date20150501_Lat-37.780075_Lon144.961513_Mpp0.597.jgw

The name of a georeference file must match the name of the image file for georeferencing to work. If you change the filename of the image you downloaded, you'll need to make matching changes to the .jgw that accompanied it.