Try again first. In addition, the analysis of the prompt' unable to open the communication port' you mentioned should be a prompt in some software, and other COM ports will be virtualized after USB to r232 line drive. It should also be modified and set to the corresponding COM virtual port number in the system device manager of the software. In addition, if the cable is too long and the power supply using USB port is insufficient, this phenomenon may also be caused. Finally, we should consider the problem of missing documents.