UPDATE:
Trying to troubleshoot this further and have performed a packet capture using a 3rd party Wi-Fi device (in monitor mode). It seems that the NANO does not reply to the probe request frames. In addition it also seems to stop transmitting beacon frames as well.
Brief extract below:
57 21:25:44 27/03/2020 3.8083188 [20720D 3903F8] [*BROADCAST] WiFi WiFi:[ ManagementProbe request] ....... RSSI = -30 dBm, Rate = 1.0 Mbps, SSID = test3
58 21:25:44 27/03/2020 3.8083373 [20720D 3903F8] [*BROADCAST] WiFi WiFi:[ ManagementProbe request] ....... RSSI = -30 dBm, Rate = 1.0 Mbps, SS