Have you tried to follow the steps of the safe update? (1st chapter of the documentation)
If not, please try that, it will most likely help.
You can find it here: http://wpdreams.gitbooks.io/ajax-search-pro-documentation/content/update_notes.html
or in the knowledge base: https://wp-dreams.com/knowledge-base/updating-from-older-versions/
If you like my products, don't forget to rate them on codecanyon :)