We have an Airport Extreme and Express. We lived overseas for years and could just plug them into an ethernet port and they worked. We moved back to NZ and I have been frustrated with the fact that I can't just plug them into an ethernet port. I spent hours on the phone with both Vodafone NZ and Apple in Australia to no avail.
So to be clear, I login to the settings of the Vodafone Hub router and swtich the Wifi 2.4 GHZ and Wif 5.0GHZ off. I connect me Aiport Extreme to the Vodafone Hub via a Lan port and that should allow me to create a network through the Apple router which I can then extend with my Aiport Extreme - is that correct?
I am nothing close to a networking expert, but broadly, yes, this is what I did. Turned WiFi off on the Vodafone Router (I have one of the older (Huawei?) ones, not a Hub, but I don't imagine it would make a difference), then an ethernet cable from the LAN port on the router to the WAN port on the Airport (the one with the circular icon), then create the network on the Airport. It is possible that some settings on your Airport that you've brought back from overseas are preventing things from happening as they should. May pay to do a factory reset of your Airport Extreme first, and then start again from scratch.