Thanks for your reply.
As I said in my last post, I already tried factory resetting the Snom 300 phone and re-provisioned using TCP several times and it still reports, "No supported media type found". However, setting the transport layer to TCP on the PBX does turn the RTP Encryption setting off on the Snom phone properly.
On the PBX, I have set the transport layer to TCP on the System, Domain and Extension level; each individually and then all together. However, the PBX continues to send a crypto line and the Snom phone does not seem to be ignoring this line.
Below is a file of all settings on the Snom phone.
https://dl.dropboxusercontent.com/u/46769109/PhoneSettings520.txt