EX6100 Connection Issues following initial set-up

I recently purchased a second Netgear AC1200 EX6110 as the last one stopped working. The first unit worked great for the first 6 months and then started disconnecting from the router despite the green 'router' light being on.

Purchased the new second unit only a week ago. Connected to the network fine. Was able to access the internet via the extended on both my laptop and phone following the set-up. The next day I realised that my phone had not received any messages. Checked the extended and all four lights were green, but both computer and phone were saying that there was no connection. I went through the wizard set-up again. It reconnected and all was well. Went out for the day, come back and again the warning comes up saying 'no internet connection'. I turned the extender off and back on and went through the wizard again and it reconnected. This issue has repeated everytime I have used the extender. It connects for the initial time when I set it up and then it loses internet connection. It shows a green light indicating it is connected to the router and when I open the wizard up it also shows that it is connected, but there is no internet. Given this is the second unit to do this, I am thinking this is soemthing that I have not configured properly. Any help would be appreciated as it is driving me a little mad!