First verify SPA finished booting. On the rear is a 'heartbeat' led with the letter A next to it. If this is blinking amber it means SPA hasn't finished booting (same goes for SPB, but then it's the led with the letter B next to it (and it's further to the left)). If this is the case, don't try to assign an IP to SPB. You need to fix the non-booting SP first. The FAQ post at the top has a section with a link to the EMC site. They have a problem solving section that may help you narrow down on the problem. Alternatively, call Dell|EMC support for assistence on troubleshooting a non-booting SP.

If however the led is off (normal state), swap the network cables and see if now SPA is seen. If so, you have a bad network cable, the cable plugged into the wrong port, or you have a configuration issue on your ethernet switch (e.g. VLAN/Vswitch not including both the management ports).