Thanks for that bug report - there were indeed some issues that script which have now been corrected.
If you update your 'steelscript-netshark' package to the latest version available (0.9.5.1) the example script should work more cleanly. You can also view what was changed via github here:
For specifying a timerange, you should probably look at the 'download.py' example instead - it has quite a few more options available.
Actually I figured it out and hopefully this reply will help others too. I used download.py to query and download pcap data from Netshark with timerange and with filters successfully, below is the explanation.
c:\> python download.py netsharkhostname --user your-username --password your-password --jobname "use Job name, dont use job id" --timerange "13:58:00 to 13:59:00" --filter ip.address=10.20.x.y --filter ip.address=10.40.x.y --filter ip.transport.port=80
The above example filters ipaddress 10.20.x.y and 10.40.x.y (these both should exist in a packet as either source or destination) along with required port , in this case 80. These filters are optional.