JSON, USB read only once

I’m reading JSON from mine Arduino. Who is connected tho the USB port.
It’s functioned a long time but sins a month it doesn’t functioned anymore and I can’t find the solution.

Wenn I plugde the USB in, the data is been readed en shows to me.
But he doesn’t refresh anymore. Wenn I plug the USB out, and in the data is refreshed, stay and do not refresh anymore again.

Can anyone help me?