Comment 3 for bug 2074070

So I looked into this and the observations made in this post is correct. It's because the default path of the wpa_cli client socket made is in /tmp (they use AF_UNIX sockets, and UDP protocol - this means the client socket must bind a visible place for the server)

/tmp is obviously not visible outside the snap, so the wpasupplicant server will never be able to respond.

The good news is that wpa_cli has a -s switch where you can change the location of the socket that the client is using. For example:

"wpa_cli -s /path/to/shared/location" should hopefully fix the issue