If you just upgraded to a new version of FactoryPMI (>= 2.x) and you had an older version of the Reporting Plugin, you’ll need to upgrade the reporting plugin with it (>=1.1.1). Upgrades are fully backward compatible and both can be done with the same unified installer.
The error message that you would have seen would look like this:
java.lang.NoSuchMethodError: com.inductiveautomation.factorypmi.plugins.reporting.beaninfo.RowSelectorTreeBeanInfo.addProp(Ljava/lang/String;Ljava/lang/String;Ljava/lang/String;ILjava/lang/Class;)V
...
...