Breakout board for EFM8BB1
You seem to be following the configuration in the application note https://www.silabs.com/documents/public/application-notes/AN124.pdf 
 
that allows you to share the C2 debug pins with RESET and GPIO.

That app note is missing the debugger part of the connection, if you see the pinout in the Debug adapter and the eval boards. https://www.silabs.com/community/mcu/8-bit/knowledge-base.entry.html/2017/03/22/using_the_usb_debug-XeTq


(Note that I didnt put the red Highlights as those are the simple connection without pin share)

Pins 5 and 6 of the table are the pin share connections, so they arent actually the same pins as your schematic shows. 

Following your original schematic: 


The node after R1 (the second D_C2CKC label) should go to a header for pin5 C2CKC_share 
The node after R2   (the second D_C2D label)should go to a header for pin6 C2D_share


So adding the pins to your J3 header:


1 Empty
2 D-GND
3 D-C2D
4 D-C2CK
5 D-C2CK_SHARE
6 D-C2D_SHARE