Do you have the 6 pin mini DIN plug and the proper jumpers installed in the Signalink USB?
I am using the SIgnalink USB and have no problems with the on the WSJT-X or Winlink etc.
Make sure that the selection for the output and input is the Audio CODEC for both and the computer is using them as well as the program.
Some use the 13 pin MiniDIN and have problems with the PTT etc.
The volume of the "Speaker" output on mine has to be 100% to drive the Signalink PTT switching and the TX volume is therefore set very low.
If you are having problems with both RX and TX then the USB setup in the computer may not be correct.
Start with getting the receive signal working into the computer and then the Transmitter (ideally into a dummy load.)
You can check it with the tune function (with the power set low and then bring it up slowly until the PTT pulls in.
You can turn on the monitor function in the IC7000 to hear what is being sent to the IC7000.
The Signal link shows up in the PC as Audio CODEC so look for that in the sound setup of your PC.