Unable to access Plusnet website

[#1]

I joined Plusnet for internet etc using their online site, via my browser.  No problems.  Now am unable to get onto the site at all, either on Opera or Edge and get this message everytime:  www.plus.net uses an unsupported protocol    - How do I access the Plusnet website please?

[#2]

I have this problem when using Chrome but it works fine with Firefox.I didn't see your message and posted about it this morning.