@Tx_Pa Hi, Please create a new APN, PDP type choose IPv4 & IPv6, keep other settings as the same. If the issue still exists, please also check if the router can get a IPv4 IP address.

@Slluxx Hi, Please download and use the corresponding model firmware for the upgrade. Besides, may I confirm why you need to upgrade the firmware? As the devices are already working normally.

@Theoldman Hi, Which powerline unit do you connect your computer to? From the screenshot, the powerline rate between the adapter and the device EFCC is only 34Mbps, if the computer is wired connected...

@Kali777 Hi, Yes, MP500 KIT can work with TL-WPA4220 KIT. They are compatible with each other.

@stelfer Hi, Did you pair the second extender with the same adapter? If you paired it with another adapter, please also connect the other adapter to the main router. You can also try resetting this...

@Jbourne Hi, Please help provide the following information: 1. Take a screenshot of the APN settings on the router. And insert the same SIM into the phone and also take a screenshot of the APN...