Facebook share button unexpectedly disappeared from product page in magento

I am developing a site magento

and I have implemented social share extension

. But after a while, the facebook

share button disappeared from the product page. The share button was used for facebook login like a button. Please suggest how can I get the button back as this button appears in the share button dropdown menu, but I need it separately along the facebook share button. I am attaching a screenshot for the same.