If this issue still exists, try these following solutions:
Some Web browsers may have cached this page by accident, you can clear the cache and history of your browser and try again.
Besides, you can also try a different browser to access http://tplinkwifi.net.
You may get the wrong DNS Server. You can use the Router's IP address http://192.168.0.1 or http://192.168.1.1 to login instead of tplinkwifi.net.
It is recommended to connect your device directly to TP-Link router with the wired Ethernet cable.
Note：For Aginet Mesh Devices, Please use http://192.168.88.1 to login instead of tplinkwifi.net.
For more solutions, please visit why fail to access tplinkwifi.net.