Wifi configuration: SSID not visible

Hey everyone,

I've got a problem with the configuration of the FLM's wifi page:

I initially installed the FLM at my own house, with my own wifi network and SSID, and here it all worked fine.

Now I'm trying to install the same FLM at the house of a client. Their local wifi network, however, does not appear in the drop-down list of SSID's the FLM can connect to... I can only connect to the networks of their neighbours? The list of networks with which my pc can connect on the other hand, does contain the required wifi network, and is much more extended than the one I can see and select on the FLM wifi page?
It also does not seem possible to manually configure the FLM's SSID?

Hopefully someone can help me out...

Best Regards