This sounds like either a disruption in your internet connection or a system freezing issue. And since it sounds like it happened at the start of the match, the match was cancelled and you are penalized appropriately. Unfortunately all disconnections and game crashes counts as leaving the match and will be penalized appropriately. The game server has no way to discern a legitimate disconnection or game crash from one that is forcefully caused by a dishonest player to bypass leaver penalties. You can learn about this policy here:
Disconnection troubleshooting:
System lockups and crashes troubleshooting: