Gransdtream GXP2000 install problems

I have installed AsteriskNow v1.02. I have set up my providers and an extension with an Xten softphone and all works well.
In trying to set up a Grandstream GPX2000 phones, I am having trouble. The phone works correctly when I answer a call with it. My problem is when I try to place a call with it. I get a continuous stream of warning messages that say:

[Aug 5 17:58:29] WARNING[3692] channel.c: Unable to find a codec translation path from g723 to ulaw
[Aug 5 17:58:29] WARNING[3692] chan_sip.c: Asked to transmit frame type 1, while native formats is 0x4 (ulaw)(4) read/write = 0x4 (ulaw)(4)/0x4 (ulaw)(4)
[Aug 5 17:58:29] WARNING[3692] chan_sip.c: Asked to transmit frame type 4, while native formats is 0x1 (g723)(1) read/write = 0x4 (ulaw)(4)/0x4 (ulaw)(4)

In addition, I can’t hear or speak on the call. Does anyone know what I’m doing wrong?

It seems that you are talking to asterisk in a different codec than what asterisk is expecting. I would check what codecs you are allowing in asterisk and then check the gxp2000’s web gui and see what codecs are selected