Do you have the latest version of QuickTime installed on your computer along with Premiere Elements, and are you running the programs as administrator?
Please state specifically what export settings you are using
and then what?
and what do you set for Presets?
and do you use the default settings for the preset selected or do you customize the export settings under the Advanced Button of the preset selected?
What is your computer player? Please be advised there is a Microsoft Windows Media Player issue with files with MPEG2 compression. If that applies to your situation, then please download and install the VLC Player to determine if the Premiere Elements export gives video and audio at playback.
Let us start here and then decide what next.
Any questions or need clarification on the above, please do not hesitate to ask.