[Plugin: Table of Contents Generator] TOC not working in my wordpress theme(2011)

Correct – the plugin doesn’t set an object key for the post called post_toc, and doesn’t advertise such.

Please follow the instructions in the readme file, specifically step 4 when editing a Page, Post or Custom Post Type from within the WordPress Administration:
– Insert the shortcode [TOC], or click the Insert Table of Contents button in the TinyMCE editor to add a table of contents to your content.

You will then see the table of contents.