Old 720 IBMi Server

I have a old 720 AS/400 (i think 9406 model) that has not been ran in a
couple of years but was working fine when put in storage and was kept in
good condition. I plugged it up the other day and the power supply fan
comes up but the front panel never lights up. I'm getting power to each
tower unit as I checked the cables coming from the power supply. What
would the next thing you would look for? Is there an internal battery that
would cause the front panel not to come on? Any guidance on what to look
for and where to look would be appreciated.

Thanks