why does everyone DIE?

If this happens on the first turn, are you sure you didn't deselect the "generate enemy empires" (or so) checkbox on the game creation "empires" page?

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sounds like there are no human controlled empires at the start......
you created an empire for yourself right?

Apparently not everybody is dead, only you!
Could it be that you surrendered by mistake??

I actually ran into this when I tried to surrender in the game which clears the plr_0001.plr file although I'm not sure if that is unintentional or a fix made to prevent people from undo'ing intentional surrenders.

For now, you can fix this bug if you did it unintentionally by deleting the .GAM file that SE V updates for each turn and its associated files and loading from the last turn. If you do not, loading from any turn before you surrendered will boot you to the main menu once the turn is processed because it cannot load the plr_0001.plr file.

Steam should auto-update the game.
its pretty weird to me.
try re-install??