Check if you have a lib/firmware/b43 directory with over a hundred files. If not, have a look at this solved thread: B43 driver seems to be installed, but no place to check "enable wifi" in new install? - #43 by 6x12 .
The solution was to install the b43-firmware pkg from AUR and reboot.
Open ‘Add/Remove Software’ (GUI of pamac not pacman!) >> klick 3 vertical dots >> Preferences > > Third Party and activate AUR Support.