Now they just work when they are in the same room?
In different rooms, since you paired them, how about status of powerline light?

They work in same and different rooms. It just stopped working in the plug where in all the top floor of my house.All lights are on in the main Powerline. In the other one, the first light flashes. The second one is stable, third one is off and last one is flashing rapidly.

Umm...the second light on both powerline adapters are on, right? You have no internet access?
Can you connnect to WPA4220's Wi-Fi successfully? If not, can you check wired connection between PC and WPA4220? Any IP address obtained?

Ok I discovered that powerline stops working when I turn my Desktop pc on.Any suggestions? I already tried disabling every net adapters in the pc but still doesn't work.It stops as soon as I press the on button.

Your PC and powerline adapter are plugged in power sockets which are near to each other?
Is it possible for you power on your PC with power extension cord (better with surge protector function) while power on the powerline adapters with wall sockets to test?

Powerline socket and PC socket are in different bedrooms. Bedrooms are near one another though. PC is connected with extension cord.When I turn on the extension core. Internet just goes crazy slow. When I turn on the PC it just doesn't work anymore.

Any other extension cord for you to test?
As I said, extension cord which has surge protector function plugging-in such equipments to the outlet can help to avoid interference.