Why laptop charger plugged in but not charging?

I have two daughters.  I bought them identical laptops at the same time.

Daughter one has always had issues similar to what you describe.

Daughter two has almost never had issues like you describe.

I believe that it is because of how they use their laptops.

Daughter one always uses her laptop on battery power until it needs to plug in and charge and then she charges it and would unplug again once it was done charging.  She also took her laptop almost everyplace she went.

Daughter two mostly uses her laptop at home, so she always leaves it plugged in and rarely uses the actual battery.   She only takes it with her if she is going someplace overnight - and even when she is at other locations, plugs it in even if she has a full battery.  (she rarely uses the actual battery)

We have replaced three charging cords and two batteries for daughter one.  We have only ever purchased one charging cord for daughter two.  This would be in a three year time span.

So - you either keep picking the worst laptops or the way you use it might be impacting the life span of your battery and charging cords.  

If your laptop is actually plugged in and yet it is still not charging, the battery might be the culprit. If so, learn about its integrity. If it's removable, take it out and press (and hold down) the power button for around 15 seconds. What this will do is drain the remaining power from your laptop.

cheap junk doesn't last

wow. are you "man handling" these things or something? That's not at all normal. I've only purchased 2 laptops in the past 12 years! and I just purchased the 2nd one recently. the first one was so old that it had an optical drive. Are you keeping this equipment indoors at room temperature? There's something YOU are doing that's just not in the normal path of a laptop. its either in the handling or the storage area. Also try keeping the charger plugged into both an A/C outlet and the laptop. in essence use the laptop most of the time via the active charger. And when you remove the charger from either end do so via the connectors. don't be tugging on the WIRES!

I've never had any issues like that.

What kind of junk are you buying?  Inquiring people want to know...so they can avoid the same mistake.  ; ' )