Update:
I have since re-installed a clean copy of emonSD 07Nov16 and expanded that onto the 8GB SD card.
I have set up a 2nd WiFi access point on my home network using a spare router and set to Channel 8.
Connected to emonPi over ethernet, registered it onto my new 2nd WiFi point and that works fine. SSH into emonPi, altered the WiFi country to GB to enable channel 13 access & rebooted. EmonPi is still connected to my 2nd wifi point on ch8 and can now see my original wifi point on channel 13. Attempt to switch to my original WiFi network on Ch13 and it refuses to connect. I have then moved my original channel 13 WiFi network down to a lower channel, but still unable to access that.
Both original and 2nd WiFi points have security options of {WPA2-PSK-CCMP][ESS]. Original wifi network SSID is “enigma”, the 2nd temp WiFi SSID is “colossus”. The passwords are alphanumeric with no special characters beyond a to z upper/lowecase and 0 to 9 numbers.
The wifi network “enigma” which is usually on ch13 is on a Draytek Vigor 2850 with mixed b,g & n modes (tried just b & g mode only too, no luck). The 2nd wifi router “colossus” is an older Thomson TG585V7 with b & g modes supported.
I own a raspberry pi zero w with stock raspbian install and that has no issues connecting to my original wifi network “enigma” using ch13 or another channel, so I can only assume there is an issue with the WiFi configurartion that is different on the emonPi distribution.
The only clue I have as to why I cannot connect to my usual WiFi network is this message in the log file:
Sep 9 17:48:02 emonpi wpa_supplicant[22779]: wlan0: CTRL-EVENT-DISCONNECTED bssid=00:1f:9f:15:0a:c3 reason=3 locally_generated=1
Full log here: https://pastebin.com/0Juxz6sD
Any ideas?