friends can't register accounts or login thru fb

I am having an issue where, if a friend wants to heart my post, he/she can't login through facebook (it doesn't work) and it also is impossible for them to register an account. I tried to help one of them but If you try to register, it either says "fill in the sections" which are all filled in, but all the words are a gray color as if it hasn't been filled in. If they try to register with the longer registration, the captcha image does not show up, regardless of browser and even with adblocker disabled. How can this be fixed so my friends can create accounts?
Thanks