USG50 to USG60 Configuration Converter

I've tried multiple times to convert the configuration file from my USG50 to the new platform using the online file converter. On uploading and applying to the new USG60, however, the wait icon spins and never completes. On reboot, the connected computer can't see the USG60, although the link light is on.

What am I missing here, and what does the converter actually do so i can attempt the conversion manually? The main reason I bought the USG60 was to avoid having to recreate my firewall configuration one entry at a time.

Thanks for any input.