WebUI display err_ssl_protocol_error

[Jonathan]

Hi,

I have a cluster of 2 R80.20 machines on open servers.

Everything was fine but suddenly I can't browse one of the members.

In Chrome I get an error:

This site can’t provide a secure connection

x.x.x.x sent an invalid response.

Try running Windows Network Diagnostics.

ERR_SSL_PROTOCOL_ERROR

In IE I get:

Can’t connect securely to this page

This might be because the site uses outdated or unsafe TLS security settings. If this keeps happening, try contacting the website’s owner.

Tried to enable all TLS options in IE and it didn't help.

I also tried Firefox but same result. 

The other cluster member has no issues, and they are identical.

What can be the problem?