My opinion is that External PCIe dock doesn't support the latest AMD GPU cards.
Found the website Blog for EXP GDC but version 8.0: http://exp-gdc.blogspot.com/2015/12/exp-gdc-beast-laptop-external.html
It shows all the Nvidia and AMD GPU cards that are compatible:
All of AMD GPU cards are Non-Supported by AMD anymore.
Make sure you have all the cables connected correctly from the laptop to the EXP GDC Dock including any PCIe GPU Power cables.
If I were you I would contact EXP GDC Manufacturer Support and ask them if the Dock supports the latest AMD GPU cards or not.
EDIT: At the same website as above it mentions which Laptops aren't compatible: http://exp-gdc.blogspot.com/2018/05/exp-gdc-compatibility-support-list.html
Since you didn't mention the Make & Model of your laptop here is the total list of compatible Laptops:
Now the above list is for version 8.0 and it probably is out-dated. So I still suggest you open a Support Ticket and ask them if the latest AMD GPU cards are compatilbe and if your laptop is compatible.
Personally I believe either your laptop or GPU are not compatible with your PCIe Dock from EXP GDC.