Nextion display can't send data

i want to display sensor data from arduino to hmi nextion. previously I had successfully displayed data to the screen in the form of a progress bar. but some time later suddenly the screen could not display data from Arduino. and i also use usb to ttl to upload the hmi program but can’t connect. please help to resolve the problem.

Welcome to the Particle community, but since this forum is neither dedicated to Nextion nor to Arduino it may be best to ask in these communities first.