Hmm. Despite following EMC’s “how-to” to the letter, we had problems bringing our NS20 back last week. If you follow the power-up procedure in “Celerra Network Server System Operation” (v. 5.6.48) it tells you to power up both SPS A and B, and both blades simultaneously. If you have power-up problems (specifically SPA not returning) try powering up SPA and Blade A first (before SPB/ Blade B).
If I’ve got some of this terminology wrong, basically bring the right hand side of the NS20 (as looking at it from the back) up before the left (so bring the DaEs up, the SPSA, then SPSB, Then Blade A, then Blade B).
This resolved our issue; SPA’s A and B came back fine, it complained about a battery discharge for a while but that resolved when it recharged.