Cause : No Data for USS (RS232 link) during Telegramm Off Time comes when the drive isn't receiving the expected data packets from the USS master device (e. g., a PLC or HMI) during a specific communication window.

F0071 fault in siemens micromaster 420 drive indicates a communication error during the USS (Universal Serial Communication) protocol. This fault means there is no response during telegram off time.

1. Check connections to the communications board. 
2. Check the master.