Hello,
I would try reinstalling the Photo Mechanic v4.6.9 application. You can download the installer from our website's Downloads page. If the new install of Photo Mechanic is unable to access the PhotoShelter site, then I recommend resetting Photo Mechanic's preference files. Please let me know what operating system you are running if you are still having problems with the PhotoShelter uploader.
Best regards,
--Bob