@zt.F 

Sorry for the inconvenience caused here, below is the compatibility list of the onemesh, while the Archer A9 is not listed there. 

https://www.tp-link.com/onemesh/compatibility/

For now, the Archer A7 V5 supports onemesh feature already, you can contact the retailer to verify whether you can return it and get an Archer A7 to work with the RE220 and build up a onemesh network.

Or you can contact the local tech support to get some help.

https://www.tp-link.com/support/contact-technical-support/#E-mail-Support

Any updates, please let us know. 

@Jimbohunt 

The Onemesh firmware for the Archer AX10 is available, please check for the update on your router web GUI/Tether app, or you can download it from the TP-Link official website, then install it manually.

You can also visit this thread we updated to get the Onemesh firmware on the router:

[New Firmware] Onemesh Firmware for Archer AX10

Note: The Onemesh firmware for the Archer AX10(EU)_V1.2 has not been officially released yet, you can download the latest version from the download link we updated in the above thread.

If you have already connected a range extender to the AX10 network, check this guide to re-build them into Onemesh network:

https://www.tp-link.com/support/faq/2509/

Let the community know if there is an issue.