This can be caused by a few things off the top of my head. You'll want to check your browser settings to allow pop-ups and third-party cookies as a new window needs to open to connect with Facebook to authenticate your Facebook login details. Another common cause is the browser may have some form of add-on or extensions that are preventing the new window from loading correctly. You'll want to check the settings for these items just disable them to see if this is what is causing this to happen.
Please give these a try and if it still isn't working, you can try loading the page up in a private window or incognito window of your browser.
If these steps do not work, I'm going to need some additional information from you to help me replicate this error.
- What OS do you have installed?
- Which browser (name and version) are you using to log into the site?
- Does this happen when you try a different browser?
