First, please check if there is no video in the recording itself or video disappears only after saving the recording to a video file.
In order to do that, please record a short sample video and check its playback in Screen Capture preview window, right after you stop the record.
If the video plays correctly in preview, then the problem is most likely linked with video codec of output format.
Try changing this codec.
To do that in the Screen Recorder 8, please click the Save as button.
If you have earlier versions of Movavi Screen Capture (7, 6 and earlier), click the white cogwheel button in the preview to access format Settings and select another codec at Video tab.
Then, close settings, save file and check playback of output video file. Also, please make sure you have necessary media codecs installed in your system - you can use this link* to download K-Lite Mega Codec Pack.
*This link leads to direct download of codec installation file from official website https://www.codecguide.com. During installation please disable additional installation options, such as installation of toolbars or system scanners - these are not required for the codec installation.
If there is no video in the preview, that means the issue occured during the recording process.
In that case please close the preview, open Settings -> Preferences -> Video menu in Screen Capture and enable Use alternative capture mode or use DirectX for capturing option.
Also, make sure that Disable Aero theme during capture option is disabled and Aero theme is enabled in your system (Windows Vista and Windows 7 only).
Close program settings and try recording the screen again, then check video playback in Screen Capture preview.
Please note that if you record video from the media player on your computer you may need to disable Overlay (Accelerated video output) option in settings of this player in order to record video properly.
Some players do not allow this (for example, Windows Media Player), so we can recommend you to use VLC player for recording video from your computer. In VLC player you can disable Overlay in Tools -> Preferences -> Video menu.
Also, some online streaming websites, for example Netflix or Amazon Prime, implement specific DRM protection that prevents video recording in certain browsers.
If you need to record video from such website, it is better to use Mozilla Firefox browser.
Please note that Movavi products do not record videos purchased on Appstore due to the copyright restrictions.