Same here. I can see the FXS plug and a softphone registering with Axon, but nothing happens when a call comes in through the FXO port, apart from the FXS phone ringing (but since it's not part of the ringing group, I assume it's just a default setting in the Linksys 3102 I'm using).
So far, I haven't found any documentation on how to set it up. Even after following the FXO Setup Guide (ie. in the PSTN Line section, "Dial Plans" sub-section, setting "Dial Plan 1" to eg. "(S0<:701@192.168.0.2:5060>😉 so that incoming calls would trigger ring group 701 (extensions 101, followed by 102))... but no message shows up in the log :-(
I keep staring at all those options in the Voice menu...