@PS0308
Hello, how about the LED on the R305 after the configuration?
Please follow the instruction to log into the web page and tell me the current hardware and firmware version.
https://www.tp-link.com/en/support/faq/1398/
If the RE305 firmware is not the latest one, please update it first.
https://www.tp-link.com/support/faq/1406/
And then please reset and reconfigure it and check whether it works.
https://www.tp-link.com/en/support/faq/1400/
Note: You can change the authentication type and encryption type of main router's wifi as AUTO.
If there is only power light on, please relogin and show us the full screenshot of the status page. And please export the system to us which you can find on the settings-system tools-system log and please tell me the model number of the main router.
Thanks in advance, and have a great day.