@Sunshine Hi, please verify the version of your MR6400 on the device label to see if it is EU or APAC version. TL-MR6400(APAC) Ver.5.30 Besides, since LTE works fine, may I know why you have to use...

@TP-Link I used 3G before, it worked. After updating the device's firmware to the latest on the website(TL-MR6400(EU)_V5.30_1.5.0 Build 221121), the router does not connect to 3G. Error 1. Maybe it's...