Re: jmeter 3.0 - not able to run in non-GUI mode, error appearing
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Check out JMeter Release Notes, especially "<a href="http://jmeter.apache.org/changes.html#Incompatible changes">Incompatible changes" section - it might be the case you are using some samplers which are deprecated or removed or your current configuration is no longer supported.
I would also recommend upgrading to JMeter 3.1 which contains new features, bug fixes and improvements.
Going forward "error appearing" is not very informative to non-telepathic JMeter users and developers, you need to include at least essential error details (most probably jmeter.log file)