FIXED! Not afraid to eat crow.... MPP engineer asked me to interchange L1 & L2.... I scoffed, but did it anyway. Immediate acceptance of grid power!... Now I thought I had a handle on electrical theory, I know phase rotation is a thing with at least 3 phases... but I was sure 2 phases was just oscillation, no 'rotation'. So much for what I thought, I'll take the result! ?