Hi Ed, I have found my solution!
Firstly, I have contacted my hosting provider, and they are unable to let modSecurity set specific rules to allow specific connections/file because my service agreement is based on a shared server (which may affect others in the server). I also do not want to set mocSec off completely because it is not the best choice. With my further research I found a documentation on WooCommerce, which change the specific .js file name, and then connect the new file name to the functions.php.
If any of you are having this problem, please review:
http://docs.woothemes.com/document/jquery-cookie-fails-to-load/
Now after enabling variations to my product, the “add to cart” button would appear.
My next step is to have the “add to cart” button to be present without choosing the variation first.
Thank you very much for drawing me to my attention.
Best,
Norma