Can you run the following commands one after the other.
sudo modprobe -r wl
sudo modprobe b43 allhwsupport=1
That should switch wifi on. To make it permanent open /etc/modules-load.d/modules.conf and add b43 underneath:
# List of modules to load at boot
b43
/etc/modprobe.d folderb43.confoptions b43 allhwsupport=1sudo pacman -S bumblebee mesa xf86-video-intel sudo mhwd -a pci nonfree 0300