Wifi extender access page blocked by privacy

I have 2x EX3110 Wifi range extenders - had them for several months, working fine. Last few weeks noticed some oddities with websites giving a security certificate error. Did some searching on this error and concluded I probably needed a firmware update for the extenders, but when I went to log in to the extenders to do the firmware update I couldn't access the login page due to a privacy error that my browser wouldn't let me get around.

I did lots of resets, tried different browsers, then tried all the steps on this page and none of it worked, still have the same error every time. Then I tried to contact support, but because I'm past my 90 days I spent 4 hours on hold and they just kept closing the online chat on me. I'm pretty desperate to get it working as my house runs on an off grid solar power system and I need the wifi to work to track the state of charge of my batteries, which I'm currently not able to do without going outside. Next step if I can't get it to work is refund and try another brand. Anyone got tips?