Hi, just purchased a TP-Link Deco XE75 Pro(3-pack) to replace my working but old ORBI 

setting up the XE75 all goes well after some retries for connection but at the end of the process there is no internet connection. The Wi-Fi seems to work well with good coverage but it will not connect to the internet. I have reset everything many times but and now close to returning the Deco. Any ideas please.