Why can not they connect in the second instance?

Hello,

                 I have 2 non-cdb instances in Oracle 12c.

         TNSNAMES.ORA:

# tnanames.ora Network Configuration File: /ora00/app/oracle/product/12.1.0/dbhome_1/network/admin/tnsnames.ora

#Generated by Oracle configuration tools.

db2 =

   (DESCRIPTION =

      (ADDRESS_LIST =

         (ADDRESS =

            (PROTOCOL=TCP)

            (HOST=xxx)

            (PORT=1521)))

   (CONNECT_DATA = (SID = db2))

)

db1 =

  (DESCRIPTION =

     (ADDRESS_LIST =

        (ADDRESS =

           (PROTOCOL=TCP)

           (HOST=xxx)

           (PORT=1521)))

  (CONNECT_DATA = (SID = db1))

)

LISTENER.ORA

# listener.ora Network Configuration File: /ora00/app/oracle/product/12.1.0/dbhome_1/network/admin/listener.ora

# Generated by Oracle configuration tools.

LISTENER=

   (DESCRIPTION_LIST=

       (DESCRIPTION=

           (ADDRESS_LIST=

               (ADDRESS=(PROTOCOL=TCP)(HOST=xxx)(PORT=1521))

           )

       )

   )

PROC=

   (DESCRIPTION_LIST=

      (ADDRESS_LIST=

         (ADDRESS=(PROTCOL=IPC)(KEY=EXTPROC0))