Head over to
https://whitedome.com.au/re4son/re4son-kernel/ and install either the "current stable" or "next" kernel.
That should sort it out.
The new Raspberry Pi 3 B+ requires updated:
- bootloader
- kernel with kernel modules
- firmware
- etc.
essentially a whole new kernel package.
Copying the firmware folder from Raspbian accross whas pretty nifty, I give you that
It won't cut it though because now you have inconsistencies between your kernel and the kernel modules - not a good state to be in
Either install the proper kernel package from the above site over the top, or - if you want to start over - install the image from that site. It comes pre-installed with the new kernel.
The "current stable" includes nexmon drivers (monitor mode might be a bit wonky on the B+ at the moment), "next" doesn't and is rock solid.
Hope that helps,
Re4son