This article explains how to troubleshoot the issue with Polls for Confluence app after upgrade/migration of the Confluence.
\uD83D\uDCD8 Instructions
Follow the below steps:
Navigate to the Confluence server installed location at this path
<confluencePath>/atlassian-confluence-7.19.18/confluence/WEB-INF/classes/velocity.properties
Modify the file
velocity.properties
.Look for the property
introspector.restrict.packages
Remove the below lines from it
com.opensymphony.xwork.util,\
com.opensymphony.xwork2.util,\
Stop and Start the server.
This workaround is required for only 7,x versions not for 8.x versions.