@DawnKC 

Hi,

thank you for your time and patience.

please try to update the firmware to be the latest one:

https://www.tp-link.com/en/support/download/tl-wa850re/v5/#Firmware

if possible, please change the wireless channel to be channel 11 for 2.4ghz;

by the way, may i know how long have you had the extender and where are you located?

Thanks a lot.

@DawnKC 

Good day,

Thank you very much for your time and patience.

Sorry for the delay.

The latest firmware of TL-WR850RE v5

TL-WA850RE(UK)_V5_181107

https://static.tp-link.com/2018/201811/20181115/TL-WA850RE_V5_181107.zip

How to update the firmware:

https://www.tp-link.com/uk/support/faq/1416/

As for the wireless channel, sorry I did not say very clearly; the range extender would flow the settings of the home router so that you might need to change the wireless channel settings on the home router;

May I know the model number of your home router?

And is there any error message when devices failed to connect 850RE?

If possible, please fetch a computer and connect it via Ethernet cable to see if the cable connection has any internet service or not;

Thanks a lot.