An appintegrator is the container of the webtemplates, which is used to display the BW reports. Creating BW reports iView from the available templates would not work unless and until the following setting is made for the iView:-
Navigate to the path
System Admin > System Config > Service Config > Browse > Applications > com.sap.portal.appintegrator > Services > Common_Configuration >
By Default it is set to false. Change this property to true and you are good to use your appintegrators, after the server restart.