"This connection Is Not Private" message I can't get past.

Hi everyone! I'm on High Sierra 10.13.6 and trying to connect to my Aruba wifi router to amend some settings. In the past I've typed in the device's IP address, entered the hardware admin password and I'm in. Today I keep getting a "This connection is not private" warning which I can't get past.

The Show Details option allows me to view the page if I enter my local admin password and create the permissions. I do this but keep getting dumped back to the warning again. If I choose "View Certificate" I see a self signed cert in there which looks like it was created a week ago - probably the last time I tried to do this. On the certificate it does state "This certificate is marked as trusted for 192.168.1.211".

Can anyone offer any help here please? How can I get onto my WiFi hub?