Hi Paul,
You can check the WiFi signal at the B2 - Maintenance menu > WiFi Strength - it needs to be at least -60dBm (-50dBm being better and -70dBm being worse).
There is more info and some tips for improving the signal on our web site -
link - How to connect to WiFi.
Please note that you'll need to keep the web UI open otherwise the B2 will go into standby when being used in NAS mode.
Paul
Brennan Support.