All In One SEO description and page name meta tags not working

On single post pages, although the post title is appearing correctly, the page description and page name meta data is not visible. I realize this glitch has been encountered many times, however I’ve searched this forum for the past few hours and have tried many of the solutions provided.

I have selected the “Autogenerate Descriptions” option and have inserted <?php wp_head(); ?> just prior to the /head tag in the index.php file (as I was unable to locate it in the header.php file as indicated). In addition, I deleted the static meta data in the header to see if that might help – however it had no effect.

Does anyone have any ideas or solutions? Thanks so much in advance.