You can restart the modem then try again. Try another web browser or device if this can't help. When you can login to the management page, check the current firmware version and hardware version....

Do you mean all lights are solid on or just several lights are on? It is normal for the lights are solid on. Make sure the dsl light and internet light are on, otherwise you won't get internet. Here...

Even the main router changes, the connection between the two adapters still exists. It has no need to pair them again. Simply connect the passthrough adapter to the new router with an Ethernet cable....

The antenna on MR6400 is for sending and receiving 4G data, not for wireless signal. Even replacing the antenna with a 5Ghz wireless antenna, the router won't have 5GHz wireless. This is limited by...

DNS is necessary to get internet. A PC set to DHCP will get a DNS server, otherwise it won't have internet. You can use DHCP reservation to bind an IP for the NAS, if the NAS needs a static IP...

This is TP-Link Forum. You can send your problem to TP-Link support.