Hello @Island-network ,

Here are the troubleshooting steps you should follow:

1) Rename the extender's Wi-Fi network (SSID) to be different from the router's
This helps prevent connection conflicts. You can find detailed instructions here: How to change wireless settings of TP-Link range extender on Tether App

2) Upgrade the extender's firmware to the latest version
Note: You can typically upgrade the firmware by connecting directly to the extender's Wi-Fi (even without internet access) and accessing its web interface. Detailed guide: How to upgrade firmware of TP-Link Range Extender

3) Compare the IP address obtained from the router and the extender
If they are not in the same network segment, enable the DHCP server on the extender. Detailed guidance: TP-Link Range Extender Not Connecting to Router: Troubleshooting Guide

Additionally, before starting these steps, please:
• Power cycle both your router and extender to refresh the connection
• Ensure MAC filtering or Access Control (Whitelist/Blacklist) is disabled on your router, as these can block the extender