When you flash a custom ROM, accidentally wipe the EFS partition, or downgrade firmware, you might corrupt these partitions. The result? Your phone loses its unique identifiers—and your network stops working. Restoring a backed-up QCN file using an is often the only fix.
Several tools allow you to read, write, and edit QCN files. Depending on your technical comfort level and your specific device model, you may choose one of the following: 1. QPST (Qualcomm Product Support Tool) Imei Qcn Tool Download