Mac Pro 10.5.6
Aperture 2.1.2
GPS2Aperture 1.0.24
Garmin Oregon 400t using gpx track logs
So my workflow is simple

open aperture
open GPS2Aperture

select an image - from Canon EOS 5D Mark 2 RAW - CR2 Format
(files are 21MB)
set minor offset on time 3 seconds
Get positions loads selected images from aperture (masters not versions in library)
Preview in GE its launches and flies to the selected image and displays it.
Click Apply and I get error

Please select images which are offline.
Alternatively if I use the viewer to try and apply the settings I get the error

Master file is not available!

This is repeatable and consistent since I bought the product it has never worked
Have sent emails but I hope some one else has seen the problem and can tell me what I am doing wrong.

Went through the whole issue with Apple assistance and moved the understanding of the issue forward. ran appcleaner to remove support files (not app) We created a new library with a single image and could load coordinates from google earth back into the aperture exif fields....hoorah!

As soon as I touched a gpx file from my Garmin Oregon 400t GPS then it started to go wrong. The only coordinates it will load are 00 00 40 00 which has been seen before, its in east africa (my picture was of ST Pauls and the millenium Bridge and after that I couldn't update as I got a "Master file not available! " So the root problem seems to be an error with the gpx handling. Is there any more I can do?

Seems its exactly the same as another thread "Calibrate or preview position puts me in Africa or on the Equator" and I see you haven't got to the bottom of that.. Would you like my Garmin GPX file and image. the images are 21M EOS 5d mark II raw files so may get blocked, let me know please.