Have you tried upgrading your kernel? Ubuntu 16.04 uses a 4.4 kernel by default. According to this
https://forums.linuxmint.com/viewtopic.php?f=59&t=229229&p=1271600#p1271600 the amdgpu-pro drivers need a 4.8 or newer kernel. I have installed them twice now (once on an FX-6300, once on a Ryzen5 1600) using a 4.8 kernel and a 4.10. I'm using Linux Mint 18.1 which is based on Ubuntu 16.04 so the process should be virtually the same. It's possible you have a different issue since you're using a mobile card but when I looked up the driver for your card I got the same one I'm using for my desktop card.
If you go to the bottom of page 2 of the above post, you'll find a complete walkthrough of the install process I used. The only changes you should need are to omit modifying the install script as it should work as written in Ubuntu and in the commands after the install that use "xed", replace it with gedit or the text editor of your choice. Of course I would use the latest driver and kernel available when you install.