M4300-48X #2 PSU

Greetings,

I purchased 1 M4300-52G and 2 M4300-48X, I also purchased the second PSU for all 3 units. I put the second PSU in the M4300-52G and it just worked as expected. Both M4300-48Xs show "Internal AC-2 Failed"? (The indicator on the front panel is flashing yellow)  I swapped the PSUs to see if it was a PSU issue, the problem stays with the #2 PSU slot. Is there something else I need to do on the M4300-48X that I didn't need to do on the M4300-52G?