If your site runs on Zen Cart 2.0.0 or 2.0.1, there are some core-file changes required for the encapsulated versions of various plugins to operate correctly on your storefront.
You can most likely simply replace (or add) a file to your site to enable an updated plugin's use. Be sure to have a backup copy of the original file, just in case the updated file causes issues on your site!
Depending on your updated plugin's directions, following is an overall list of the various Zen Cart base files that were changed in the zc201 to zc210 transition to enable additional features in encapsulated plugins.
This file, updated in releases following Zen Cart 2.0.0 via PR 6462 enables an encapsulated plugin to provide additional AJAX handlers.