Hello Farid,
This error comes up often when the STM32-Primer is not correctly connected to the PC. You should :
1. Check that an USB cable connects your PC to the DEBUG mini-USB connector on the Primer
2. Push the orange button on the Primer to power it up
3. You can check in Windows Device Manager that the RLink appears in the Jungo section. If it does not, the driver is probably badly installed
4. Try again to program your Primer.
Lionel