I have a problem with login Facebook

Let us know the webpage url where you are facing this issue, so that we can help you out.

My site: https://www.kinhdoanhsi.vn/
Thank you

And other Social logon icons are appearing but not Facebook in firefox

Kindly update your plugin to just released version 7.8.1. This should fix the issue.
If Facebook icon doesn’t appear in Firefox, add following CSS in Custom CSS option at Super Socializer > General Options page in admin area:

.theChampFacebookLogin{
	display: block !important;
}