This kb explain a situation where a customer might report all interface on EX2300-48P are in down state. 

• All interface are down.

                    Physical interface: ge-0/0/0, Enabled, Physical link is Down

         Physical interface: ge-0/0/1, Enabled, Physical link is Down

         Physical interface: ge-0/0/2, Enabled, Physical link is Down

• we can see all interface are configured for PoE and No consumption by PoE.

root@Switch> show poe controller

Controller Maximum  Power     Guard  Management  Status    Lldp

index    power   consumption  band                Priority

  0    750W   0.00W      0W   Class    AT_MODE    Disabled

root@Switch> show configuration poe

interface all;

interface ge-0/0/1;

root@Switch> show poe interface

Interface  Admin    Oper  Pair/Mode Max    Priority    Power     Class

 status   status    status          power          consumption

 ge-0/0/0  Enabled   OFF   2P/AT   15.4W   Low      0.0W      not-applicable

 ge-0/0/1  Enabled   OFF   2P/AT   30.0W   Low      0.0W      not-applicable

 ge-0/0/2  Enabled   OFF   2P/AT   15.4W   Low      0.0W      not-applicable

 ge-0/0/3  Enabled   OFF   2P/AT   15.4W   Low      0.0W      not-applicable

• We have observed below error on all interface.

Jul 8 07:28:25 CHASSISD_UI_POE_ERR: PoE port name ge-0/0/0 status 18

Jul 8 07:28:25 CHASSISD_UI_POE_ERR: PoE port name ge-0/0/1 status 18

Jul 8 07:28:25 CHASSISD_UI_POE_ERR: PoE port name ge-0/0/2 status 18

Status 18 indicates the (hex value 0x18) Port is off: Internal hardware fault Port does not respond, hardware fault, or system initialization.