Prefer send an email to their support for further help. If there is no success, it's convenient for you to get a replacement.

This is just a SOHO wireless router which don't support that feature.

Check whether the Device Time is the same as your smart phone. If it's not, go to Home page and click on menu on the left top. Go to Settings and click Location & Time to sync your time zone.

Hey, here is a explanation about this: https://www.tp-link.com/us/faq-2118.html

It's better to provide your model number of range extender. you can also login to web UI to configure it according to the Quick Installation Guide.

restart the Re and try again. Besdies, make sure you do connect to the RE456's Wi-Fi.