not displaying images in posts or media library

Hi,

I have had a sudden issue with WP 3.9.1 stopping displaying images in posts, media libary and the default header image in the Graphene theme on my site https://how-to-lower-your-blood-pressure.com. Images are shown in widgets. The image URLs are shown in the posts, it is just that they are not being displayed.

I do not have any plugins on this site that control how and where images are stored or displayed. Nor hasve I changed any of the theme’s settings.

I have searched this forum and the Internet for a solution and I have tried almost all of the suggestions. I have not tinkered with the HTACCESS file as I do not know where it is, and if i did, I would not know what to do. Nor have I tinkered with any CSS files for the same reasons.

I have done the following, but to no avaial:

1. I have changed the file permissions to 777, which did not work, so I restored the 755 values;
2. I deactivated all plugins – did not work;
3. I deleted the post I was making that first made me aware of the issue – it made no difference;
4. I am using the default upload directory and upoads are divided into yearly etc. folders I have unticked this box on the dashboard, which made no difference, so I ticked it again.
5. I unticked the thumbnail size box (Dashboard>settings>media), which made no difference, so I ticked it again;
6. I reinstalled WP 3.9.1 using the reistall button on the dashboard. It made no difference;
7. I changed the theme from Graphene to Twenty Thirteen. That made did not fix the problem although it did confirm that it was not related to the theme, so I changed back to Graphene;
8. My ISP say they have not made any changes to the server and pointed out that I have other sites on the same server each using WP 3.9.1 and which have the same file permissions and are working fine;
9. I deleted the themes I am not using, just in case there is a conflict. That did not work;
10. Although it should have no bearing on the issue, I deleted all users other than the administrator. They could not make any posts or comment anyway and were just spammers. As expected that had no effect.
11. I cleared my browser’s cache several times. I am using Thunderbird. That made no differnce either.

This is not a problem that is unique to me. Does any one have a solution to this problem that I have not tried?

Thanking you in advance for your help.