If that saved game was from 0.70.274272 it's probably not compatible with the update (0.70.274685).  There's no way to go back to 0.70.274272 since the non-Test version is still on 0.65.

The update was to the Test version.  The non-test version has never updated to 0.70.  It will still load the 0.65 version which won't run your 0.70.274272 saved game either.

The problem is that EPIC does an automatic update to your game files when you open a new session once Stardock has posted a new version, but that doesn't update your saved games.  They are only compatible with the older version of 0.70.  There is nothing you can do to make them run on the updated version.

I posted on discord but thought i should post in here as well - the 'toxic leader' event seems to pop up far too often and equally its affects seem to end up affecting ALL of your leaders - i ended up having to quit a game as my governors were all becoming disloyal from it! (i wondered why my planets were so unhappy!)

SSStreetFighter - Now I understand why you were so upset about losing that game.  I totally agree that you shouldn't try doing content on an Alpha game, especially not Stardock.  Even their Beta's tend to be fast moving targets.  Good luck and please check in from time to time to see how the game is progressing.  It looks pretty promising to me!