@MarkL057 Seems as if you know what you are doing. I'm not going to be much more help unfortunately, someone else on here may have an idea. Did you restart the ONT and possible try asking Giganet...

@MarkL057 Not 100% sure, Giganet is quiet a straightforward setup on a 3rd party router. What settings did Giganet give you to put in the AX53? Can you list them?

@MarkL057 Could you use these apps when the Eero 6E pro was connected, just to rule out it may be an issue with the ISP?

Ebay is good for buying single units as some people sell off "surplus" units they don't need.

@friedeggs Correct, your main deco can connect direct to the ONT via ethernet cable. You will need to amend the connection type on the deco app to PPPoE which will also require your Plusnet username...

@DavidR1974 What connection type is your AX55 using if that is working?