Converting files between Altium Designer and Circuit Studio board layout file
To open an Altium Designer PCB document in CircuitStudio do the following:


In Altium Designer Save your PCB as a PCB 5.0 binary file. Do this by going 
to file > save as > from the pulldown menu choose PCB5.0 Binary
In CircuitStudio go to file > import and choose the PCB5.0 binary file you 
just created. 


that should work.

If you're using Altium Designer 18 (which I know you are not currently using) you would just need to go to file > export and choose CircuitStudio (in Altium Designer).