RE: Dell Inspiron 5555 (Plugged in, Not charging).
Was this purchased as a new system? It's not a current one - you should check to verify whether it's in warranty or not (it will need to be registered with Dell to activate the warranty):
This is a 2015 model system so even if it's new to you, it may or may not have a remaining warranty.
If the system is OUT of warranty, go into Setup (F2 at powerup) and check to make sure the AC adapter is listed there -- if it shows "unknown", the battery will not charge. In that case, the first thing to try is a new OEM Dell AC adapter. If that doesn't solve the problem, the DC jack is next to replace:
And if that doesn't solve the problem, replace the mainboard.
If the adapter IS recognized, will the battery charge when the system is powered off? If it will, but won't when operating, it may be a Windows driver problem or setting.
If the system WILL NOT charge when powered off and the adapter IS recognized, chances are it's a bad battery.