I think the only way this can work in your Spa is to put the extention of your IMS registered with Axon in your Spa.
email@example.com did not work for me
192.168.xxx.xxx@197 did not work
192.168.xxx.xxx:606 did not work
Make sure that extention 197 or whatever you have chosen to use for your MOH is registered with Axon.
To see if it is registered login to your Axon web control panel, select extentions and look under Status, if you see
sip:firstname.lastname@example.org:port then you have sucessfully registered IMS with Axon.
If you don't see the status for extention 197, then do the following.
First shut down both Axon and IMS, then restart IMS first waite a few seconds and then Axon. (This is just one of the solutions I used to get me going)
From you Spa phone dial 197, if you hear music on hold, then you are in business the rest is up to you how you can use the hold button is it's difrent from phone to phone.
Hope this will help or at least get you in some directions, if it work please hola back!!!