Gallery Videos Black Screen
Suggested fix (unconfirmed): Install the required media codecs (like the Windows Media Feature Pack or Linux restricted extras) or update your GPU drivers. If that fails, play the videos through a web browser using a VPN.

2 fixes · 1 how-to answers · Steam discussions
Suggested fix (unconfirmed): Install the required media codecs (like the Windows Media Feature Pack or Linux restricted extras) or update your GPU drivers. If that fails, play the videos through a web browser using a VPN.
Suggested fix (unconfirmed): Verify the game files through Steam and run the game as an administrator.
Suggested fix (unconfirmed): Press Alt+Enter while the game is running, or add `-windowed` to the Steam launch options.