When you have a problem connecting to the AS400 server after a power cut / power surge the most likely culprit is the network card.
The first thing you should check is obviously the connection m reboot switch, check id cable is correct, then check if lights on the network card is on. if it is on than enter directly on the server, click on GO TCPADM m there you can choose the various options the first one being 5 and eneter when selected *ALL .
If the lights are off first the last steps and if still not working than open the server , take off the network card and reinstall it, then back to the process on top. but if the lights on network card still not on than the most likely is the card is done for.
Rememeber to be very patient as it can take upto 30 minutes for the server to work fully.
Update: another step to do before takeing the network card and putting it back in is to go from main menu WRKLIND put number 8 next to ethline option , if it is active than first deactivate puting number 2 next to the first line ethline and number 1 to activate once it is changed, pressing F5 will refresh the page.