Alan

Sounds more like a corrupt or incorrect .htaccess file somewhere, or worse still a server configuration issue.

Who is your host?

Appearance –> Menus

I would ask the person who normally deals with your website / hosting to have a look.

However it may be a Godaddy issue, they have had some problems today apparently..

Have you contacted whoever hosts the website, to check their status?

Sounds like your database server is down or you have the wrong details for it in the config..

It means the webserver can not find an index file (index.php etc) in the directory.

You may have a Linux server but have you checked the webserver that runs on it, usually Apache..

Login via FTP and delete the folder containing the SEO plugin (/wp-content/plugins/wordpress-seo). Then login again and WordPress should deactivate the problem plugin.

Who hosts her website?

I take it you tried a different browser, just to be sure..

Is Apache (or what ever webserver you use) actually running?

That error is normally, browser can’t reach website, type of error..

What error are you getting on your other domains? 500??

The only way to tell if a plugin does what you want is to try it.

But don’t install lots, install one at a time and play with it. If it does not do what you want, un-install it and try something else.

Some plugins can conflict with each other, so best to try them separately.

The website works fine in http just not https

https://www.aednet.org/

So is the secure hosting setup properly?

Is this the correct website https://74.93.88.147/

If so then looks like a server config issue.