What are the settings in ArcPad > GPS Preferences > GPS on your Geo 3000 unit? What are the Serial Port Parameters (accessed via ? Is the NMEA port setting reading GSV sentence? Often the empty skyplot can be resolved by resetting NMEA GPS protocol in Trimble's GPS Controller software, http://www.trimble.com/support_trl.asp?Nav=Collection-31616.
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If after modifying settings you still have an empty skyplot in ArcPad, please submit a support interaction with Esri Support via phone, email, web for or chat options.