@mrt88 If ES is just naming the device to configure as keyboard, you haven't switched the mode of the IPac. If it would be in one of the gamepad modes, ES would say something like "# gamepad(s) detected..."
AFAIK the mode is persistent once set and if possible you may well keep to @hopwon and change the mode to your desired one on a windows machine/observed checked via winipac.
Once it reports itself as 2 gamepads.... as I had downgraded (after updating from 1.39) my Firmware from the 1.5? to 1.49 (KBD only) I can't try it out and really don't recall how the multi-mode DInput/XInput differs for P1/P2 - Opening the configure input from emulation station I 1st would configure the parts connected to the P1 side of the I-PAC2 and see whether the P2 side responds afterwards (so both pseudo-devices are using the same identifier), but my guess would be that you have to configure the input again with the stick/buttons connected to the P2 side of the I-Pac [1].
Edit: If you opt for the "Keyboard" way, manual editing configs is the only way (AFAIK) of setting the keys for player 2+. The Docs @mitu linked to are pretty good, in addition you may have a look at this (maybe somewhat old) guide from theink. And the meta/shift-key from the IPac2 was one of the main reasons I switched back to keyboard only mode, as it opens up so much possibilities in key-assignment that I am unsure how to achieve the same from within a gamepad mode of the I-Pac.
1: Would be wise on ultimarcs behalve to report P1/P2 sides of the IPac (in Gamepad(s) Mode) with different IDs, as both parts could be configured in a different way/layout button assignment via Winipac.