@Sentinel2A You need to provide more info for someone to help with troubleshooting. Multiple things come to mind: Deco mesh bandwidth settings restricts traffic, device negotiated 10Mbps Ethernet...

@KuroYami The way to resolve this is to configure Deco mesh to run in Access Point mode: How to set up Deco to work in Access Point mode In this configuration, your ISP router will provide IPv6...

@CHF_UK Very helpful summary of investigation. For those who plan to troubleshoot their Deco mesh, you can get quick glance of signal strength for each of your Satellite Deco units, in single place...

@Nyist According to his document, enabling Network Management gives Manager all necessary rights: https://www.tp-link.com/en/support/faq/1444/ Please double check that Network Management is shown as...

@Ttrax I would recommend getting X95 and making it Main Deco. It should be fully compatible with your X90 mesh, it is tri-band, and it has an extra Ethernet port: three in total comparing to two X90...

@Daniel9789 About connection preference - sorry, missed the fact X60 does not support it yet. I doubt we will see its firmware upgraded soon to have that feature: TP-Link haven't released even beta...