The error you shared is more generic one, it will be shown only when the processor is not able to run with the given configurations.
Can you once make sure all the configurations you have used in the processor are correct i.e port information etc.
lets for example i have shared configs for ListHDFS processor below.
This processor requires Hadoop Configurations Resources to run but they are not Mandatory properties.
if you won't mention hdfs-site.xml,core-site.xml in Hadoop Configurations Resources, this processor results same error as you shared above.
Like this way you need to figure out what are all the configurations you need to mention in ListenUDP processor as they are not Mandatory properties. Those missing properties will also results to same error as you are having now.