With recent updates to snom firmware, it's apparent some users are having to initiate the same call twice before it connects, this is linked with an issue where the snom is selecting an incorrect codec to initiate the call. To resolve this you will need to access the web interface of the phone.
Accessing the web interface requires you to enter the IP address of the phone in your web browser. If you are unsure of the IP address of your device then please see the relevant guide in this knowledge base, or refer to the instruction manual that came with the device.
Please note that if you purchased the phone from Gradwell you will be prompted for a username and password. Details on how to find this can be found in this article.
Once you have logged in, click on the account that you are having the problems with (in most cases this will be Identity 1).
From here, click on the RTP tab.
This brings up the codecs that the phone tries to use. A codec is used to compress the audio that your phone sends to our platform, and it is essential that you use ones that are compatible with our system. Our default codec is called G711, however we also have an alternative codec called G729 that can be used if you are experiencing call quality problems.
On the RTP page ensure all the codec dropdown boxes are set to G.711u, apart from the last option which can be set to G729 (please note that if you wish to use G729 this should be set as Codec 1, with the other fields set to G.711u).
Please also ensure that RTP encryption is set to Off. Once done click Save.
It's also worth checking that the call initiate method is set to Asterisk. to do this, click the SIP tab and then ensure that Server Type Support is set to Asterisk.
Click Save, and then reboot the phone.