TL-MR6400(APAC) v5.30.    I had old software on my PC. I downloaded the new software from the TP-Link website. I installed it via the web interface. Then it gave a "SIM card not found" error. The SIM card is no longer being read. The ISP is gone. I want to revert to the old version, but it keeps giving me an error. It constantly gives "error:1" and freezes. We need to find a solution to this.