Posts not displaying since WP 4.0 migration – redirect to (non-WordPress) home p

Good day,
WordPress automatically installed yesterday on my site and since then I have been unable to view posts – they re-direct to my (non-WordPress) home page.

I can log into and access my site perfectly.
All posts show up perfectly in the Posts listing.
I can Edit them perfectly in WordPress.
But when I view them, the URL is correct in the address bar, but the post does not display, only my home page.

This appears to have been a gradual process. Last night, only older posts were affected. Now it applies to all my posts.

My site: https://www.ecofriendlylink.com (home page – not wordpress)
My blog: https://www.ecofriendlylink.com/blog (WordPress)

Example: https://www.ecofriendlylink.com/blog/use-lemons is a recent blog post which does not display in my wordpress blog. It shows the correct URL in the address bar but displays the (non-wordpress) home page.

I have disabled all (yes, all) of my plugins, and cleared the cache. The problem remains the same.

I’ll have to restore from backup to go back to the previous version of WP as I can’t have my site effectively down, but I’ll wait a while to see if anyone knows about this issue – I’ve searched but haven’t found anything similar.

Thanks in advance for your help!