My car ('90 civic) has been sitting for about a month now and I just fixed it but car suddenly died and now I have no power even with jumper cables attached.

What was going on when it died? Were you driving? Was there any noises?

Test the under hood and under dash fuses with a test light or multimeter--this particularly goes for the large box fuses in the under hood fuse/relay box. After that, test the ignition switch for wear, pitting, or melting.

My bet is that the battery is bad. Remove and fully charge, or replace, the battery. Most auto parts stores will test and charge batteries for free.

What was going on when it died? Were you driving? Was there any noises?

I was driving it and it died before I could even leave the driveway, then went to jump it again and not getting any power even while jumpers is connected.

Have you checked your battery itself and the alternator?

A volt meter will make quick work of this, Try head lights first. Then voltage at battery, then from battery positive and negative on ground on block and chassis. If you have it that far come back.
Battery and both positive and negative cables need to be checked at both ends.

Car was sitting. Jumped it to move it so we could work on it. Car started, held the charge, moved it to the garage. Did some work on it, cap, rotor, plugs, wires. Jumped it again, went down the driveway. Car died, now cannot even jump.No power at all

have you checked your battery itself and the alternator?

If you have a dead battery there not if fire going toyour ignition system and will not stay running get a new battery . Chicoman

Or as the Rastas say, "You need a Metermon". You can see where you have power and when it is lost.