For a few months now I've been unable to remotely access 2830 ADSL routers using HTTPS. I also get this on a 2850.

The error I get in Internet Explorer is:

'This page can’t be displayed. Turn on TLS 1.0, TLS 1.1, and TLS 1.2 in Advanced settings and try connecting to https://nnn.nnn.nnn.nnn:nnn again. If this error persists, contact your site administrator.' (IP:port obscured)

IE does have TLS 1.0, 1.1 & 1.2 on.

When I try Chrome, I get the following:

'This web page is not available. ERR_SSL_VERSION_OR_CIPHER_MISMATCH.
A secure connection cannot be established because this site uses an unsupported protocol.'

What do I need to do to regain remote access to these routers?

Thanks

System Maintenance >> Management
DEselect (UNtick) Enable SSL 3.0

If the option is not available, apply newer firmware update

Thanks, that worked. I had to upgrade the router and disabled the TLS/SSL option.

In Chrome I can now reach the router though it issues the following message... 'Your connection is not private. Attackers might be trying to steal your information from nnn.nnn.nnn.nnn (for example, passwords, messages or credit cards). NET::ERR_CERT_AUTHORITY_INVALID'.

I click on advanced option displayed, then 'proceed to nnn.nnn.nnn.nnn (unsafe)' and it works.

In IE, I get a certificate error too, and can proceed.

Is there anything I can about the certificate error?

That's for all routers, don't worry.
The certificate was issued by Draytek router and not by some authority.