I had the issue on 3.8.9.1 which was when it first stopped working for me, although it took me a while to realise it.
I upgraded to 3.8.9.2 after I saw in the release notes it fixed the web interface, however in my case even after a factory reset it doesn't allow remote management over WAN. The furthest I can get is a half loaded login page.
Not going to raise a support request over it as all they do is ask take a week to reply and then ask for log files. Must be something related to the settings I am using if other people have it working on 3.8.9.2.
I am using default port (443), one non standard setting it could be is that I have enabled brute force protection so it could be that borking it.
