Generally I hate these warnings because they are extremely stubborn while not really telling the user what could fix the problem. They also don’t explain why the error might show up today when everything was fine yesterday.
I’d much prefer a message like: “There is no way to verify that this site really is who it claims to be (possibly due to an expiration date, as sites must periodically renew their validations). The owner of the real site can resolve this error by using certification services such as LetsEncrypt. A secure connection is not possible until the site renews its validation.”.
The user in this case is a random web browser piloted by a non-technical person. It doesn't make any sense to try to arm them with technical solutions to the problem; that's the site owner's job.
What I find really interesting is the website in question, oilandgasinternational.com, now has SSL on by default now; it'll redirect you from any page if accessed over HTTP. Given that, perhaps we should just let them complain? It seems to raise awareness over the need for SSL.
I’d much prefer a message like: “There is no way to verify that this site really is who it claims to be (possibly due to an expiration date, as sites must periodically renew their validations). The owner of the real site can resolve this error by using certification services such as LetsEncrypt. A secure connection is not possible until the site renews its validation.”.