Serial number device not present!

Hi everyone, I get this message from ACLI 

 

Notifications:
- Serial number device not present! Re-insertion and reboot required!

 

 

I noticed that 'cause the SBC started to reject the calls with 503

 

And I saw this:

 

ACMEWRPLZ# sh features
Total session capacity: 0
Enabled features:
none

 

ACMEWRPLZ(license)# sh
License #1: SIP, H323, IWF, QOS, ACP, Routing, Load Balancing, Accounting,
High Availability, ENUM, DoS, IDS, IDS Advanced
no expiration
installed at 12:36:16 May 20 2013
Total session capacity: 0

 

 

SBC details

 

ACMEWRPLZ# sh version
ACME Net-Net OSVM Firmware SCZ6.3.9 Patch 2 (Build 286)
Build Date=07/12/12

 

 

I rebooted the SBC and that solved the problem but what would be the problem?