BT Home Hub no longer connects with android phone

I have been happily using a generic android version 5.1 mobile to connect to my BT home hub for more than a year . Suddenly my phone no longer connects to my home hub whilst other devices in house still do( Sky box,tablets etc) including other android phones. I can access the home hub and see that my mobile is connected but no IP is provided. The error message against IP address is "This device either does not support or is not configured for IPv4 addressing.". Likewise for IPv6 message is "The Smart Hub is currently not enabled for IPv6 addressing".
I guess the android phone has an issue with IP addresses . I can see correct MACaddress and phone can connect via BT Fon.
Help appreciated please in trying to reconnect android phone to my BT Home Hub6.

Silly question, have you tried a full power off/reboot of the phone?

As well as a battery out to force full restart on phone, sometimes making them forget existing networks can help with these oddities

my HH6 always used to (at random) deny devices access and I had to either reboot it or swap to a HH5. It was always the 6 though that had the problem.

So in the end I just bought some cheap home plugs and Ether netted everything.

Rebooting the mobile and home hub doesn't work . I managed to isolate issue to the phone itself and only solution was to reset it to factory settings. Scary but remarkably painless other than having to re-enter every password used for eacg app etc.
All sorted now.