Plusnet Hub Two - with BT Home Hotspot 600's - IP address

[#1]

My mum used to have BT Broadband, with 2 BT Home Hotspot 600 plug-in powerline devices, which we bought from PC World, to extend the signal throughout the house.
She's recently switched to Plusnet and has a Plusnet Hub Two, which is working well. On unplugging and replugging in an existing Hotspot, we can get all the lights to show green, and e.g. my phone can see the Hotspot exists. However, when we try to connect to it, it eventually fails, saying it can't get the IP address.
Any suggestions, please?

[#2]

@Aceandrew  Welcome to the Community 
Factory reset the Powerline devices and set rhem up again from scratch

[#3]

"@Aceandrew Welcome to the Community
Factory reset the Powerline devices and set rhem up again from scratch"

Thanks for your suggestion. I thought I'd essentially tried this yesterday, but I tried again today. I unplugged everything, held the Link button on the wired Extender for 15 seconds, and pushed the Reset button on the Hotspot, as recommended.
Unfortunately, although all the lights are showing green on everything, we are still getting Connection Failed when trying to connect to the Hotspots on our phones.
Any other ideas, please?

[#4 · Accepted solution]

Is one of these extender units wired to your Hub Two?

If so, which port on the back of the router do you have it plugged into?

[#5]

"If so, which port on the back of the router do you have it plugged into?"

Thank you: Your question has solved it!
There are 4 similar-looking sockets labelled 1, 2, 3, and WAN. My mum had plugged it into WAN, but when I plugged it into one of the others instead, it started working properly. 😀