Oracle listener not running and won't start

I had the same problem. Solution in my case: run CMD as ADMINISTRATOR. then type and execute: "lsnrctl start" wait about 2 minutes then should work. (in my case was only 50 seconds, but just to be on the safe side)

I solved it by updating listener.ora file inside oracle directory oraclexe\app\oracle\product\11.2.0\server\network\ADMIN.

Why did it happen to me was because I changed my system name but inside listener.ora there was old name for HOST.

This might be one of the reasons... for those who still face such issue might think of this possibility as well.

1.Check the Environment variables (must be set for System and not for user):

ORACLE_HOME = C:\oraclexe\app\oracle\product\11.2.0\server
ORACLE_SID = XE

2.Check if you have the right definition in listener.ora

XE =
  (DESCRIPTION_LIST =
    (DESCRIPTION =
      (ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC1))
      (ADDRESS = (PROTOCOL = TCP)(HOST = localhost)(PORT = 1521))
    )
  )

DEFAULT_SERVICE_LISTENER = (XE)

3.Restart the service (Services > OracleServiceXE)

After that you may see a new service called OracleXETNSListenerXE.
There is already an old OracleXETNSListener.

I started both and then I was able to make a successful connection.

Edit:

If everything is running but you still can't connect, check if there is no error: ORA-12557: TNS:protocol adapter not loadable.

To correct the error go back to the Environment variables and this time edit the one called: Path. Be sure that C:\oraclexe\app\oracle\product\11.2.0\server\bin is somewhere at the beginning, definitely before any other path pointing to a different version of the Oracle DB.