Did you put a comma between the two expressions? Testing locally
.es(interval=1d, index=session_data, metric=cardinality:player_id).label('Unique Players Logged') .es(index=gameplay_stat, metric=cardinality:game.player).label('Unique Players Played')
gave me the error you posted, but
.es(interval=1d, index=session_data, metric=cardinality:player_id).label('Unique Players Logged'), .es(index=gameplay_stat, metric=cardinality:game.player).label('Unique Players Played')
works fine for me.