Yes there is a slight problem – the taxonamy is set to post_category. If you trying to display blog posts, it should be category. See examples below. Thanks
[show_post_snippets number_of_columns=3 post_count=9 image_size='large' show_meta='false' post_type="post" terms="opportunities" taxonamy="category"]
or if displaying portfolio items =
[show_post_snippets number_of_columns=3 post_count=9 image_size='large' show_meta='false' post_type="portfolio" terms="opportunities" taxonamy="portfolio_category"]