Snom 320 doesn't register

I have a Snom 320 connected via a switch to an Asterisk server.
The sip.conf and extensions.conf are according me correct ( I checked with samples on different sites ). The Snom 320 is dhcp enabled and has an account 1001 configured and a registrar 192.168.0.5 ( the asterisk server ).
First I start the asterisk server till it is up and running.
After, I powered the Snom 320. In the display of the Snom I see it receives an IP-address and a netmask.
In the Asterisk console I entered “sip show peers” and “sip show registry” and I see that nothing is online and offline and nothing is registered.

Questions:

  1. What is the communication process between the startup of the Snom and the Asterisk server with respect to the config files.
  2. Is there anything more in the Snom I have to configure to let the registering be succesfull ?

THX !