Tips: Cannot connect to Facebook Chat - friends online are not displayed.

The integration of Facebook Chat into the messaging hub is one of the selling points of Windows Phone since the release of Mango or Windows Phone 7.5 a bit less than two years ago. Starting a conversation on Facebook and then seamlessly switch to SMS in case of a loss of connectivity is awesome and unique to the Windows Phone platform. But as with everything in the world of technology, and no matter how good the technology is, it also breaks. It occurred to me at least once, where Facebook Chat will not connect or will not display my list of friends who are online. Facebook website will display my friends available for chatting, but not the app. How do you solve that problem without a hard reset or throwing the phone out the window from a ten storey building, which equals to an extreme version of a physical hard reset.
The process to solve this problem is simple and straight forward. Let's start with the phone.

1. Go to Settings > email+accounts and delete the Facebook account. Press and hold on Facebook and press Delete.
2. Now we need to let Windows Live/Microsoft Account know that we've removed Facebook from our phone. So press and hold on Windows Live/Microsoft Account and select sync. At this point, we're done with the phone, for now.
3. Log on to profile.live.com on a PC.
4. Click Manage
5. Click Edit under Facebook.
6. At the bottom of the screen, click "Remove this connection completely".

Stay with me as we're almost done. At least on the PC where you can sign out of your profile page. Let's now go back to the phone. The next step consists of simply re-adding the Facebook account to the phone.

1. If you're not there already, go to Settings > email+accounts.
2. Tap "add an account" and select Facebook
3. Tap the Email address box, and then type the email address that is associated with your Facebook account.
4. Tap the Password box, and then type your Facebook password.
5. Tap sign in.
6. If you haven't linked your Facebook account to your Windows Live ID, you'll be asked if you'd like to link them now. Tap Connect to go to a Facebook website
7. Follow the instruction to connect your account.
8. Finally, we need to verify that Facebook Chat is enabled on the phone. This setting is found in Settings > Messaging for both Windows Phone 7.5 and 8.

Start messaging and swipe to the left to access Facebook Chat and voilà; all your contacts are back, at least those who are online, and your status is now set as available.
The above steps have worked for me and users on the Microsoft Answers Forums. In the unlikely event that it doesn't fix your issue, let me know in the comment area or use the Microsoft Forums.