Nucleo L152RE and S2LP: debugger connection lost with using sigfox

[TMARI.1]

I used nucleo-L152RE and S2LP S2868A1. My device was connected with the Sigfox network. I ran the application Sigfox push button demo. When I want to debug the code and pushed the button, the console reported to me this following message :

Target is not responding, retrying ...

Error! Failed to read target status

Debugger connection lost.

Shutting down....

I tried to solve this problem step by step with the debugger, and I found that the connection was lost when the following function was executed :

   

/* Call the send_frame function */

SIGFOX_API_send_frame(customer_data,4,customer_resp,2,0);

I used STM32CubeIDE V1.2.0

How can I keep the debugger connection ?

Thanks for you help!