From autoplot.org

Required Java Version

Java 1.7 is required to run Autoplot, but Java 1.8.0u102 is required to access data from CDAWeb. The problem is the signature used by NASA/Goddard is not compatible with older versions of Java. While it may be possible to use an older version of Java to access CDAWeb, it may be easiest to simply update Java.

To update your Java, see http://java.com.

Note Java 1.8 will be required for all users later Spring 2017.