More recent Security and Antivirus software such as Bitdefender 2018 have built-in Webcam Protection features that may prevent XSplit from displaying your webcam properly.
Normally, you will be prompted by Bitdefender when XSplit tries to access your webcam and you can choose to instantly exclude XSplit from webcam protection. If this is not the case, you will need to manually change your webcam protection settings as shown below.
Allowing XSplit webcam access in Bitdefender 2018
Open Bitdefender and go to the Privacy tab by clicking the icon.
Click VIEW FEATURES.
Click Webcam access under the WEBCAM PROTECTION panel.
Click on the Access toggles to the right of the XSplit applications you use.
You can also manually add XSplit as trusted applications for webcam access.
On the Webcam Access screen, click Add a new application to list.
Select and browse for XSplit.Core.exe in your XSplit Broadcaster installation folder then click OK.
Select and browse for XSplit.Gamecaster.exe in your XSplit Gamecaster installation folder then click OK.
¹If you are using the PTR version of XSplit Broadcaster, the default installation folder and file will be found in C:\Program Files (x86)\SplitmediaLabs\XSplit Broadcaster PTR\x64\XSplit.Core.exe.