Ever since 3.9.1, WordPress has become unusable

You’ve either got PHP errors or Javascript conflicts. The blank pages are what happens when there’s problems with some of the PHP code on the iste, and the other things that you said are all symptoms of Javascript issues.

To check the PHP errors, change this line in the wp-config.php file:

define('WP_DEBUG', true);

That will allow WordPress to show the errors that are happening for the blank pages.

For the rest, you’ll need to use FirBug or your browsers devleopers tools to go through the Javascript side of things and see what errors are coming up in the console. Debugging Javascript is a lot harder, but can be done.

Does it narrow it down to say that I have a subdomain with WordPress installed that isn’t having any issues?

Weirdly, the blank pages cleared up own their own a few days ago (nothing I did I’m sure), and I’m left with the plugins being glitchy & not being able to insert photos onto the frontend.

I’ve just tried changing the wp-config.php file, and I started getting these on all the pages, front & backend:

Notice: Undefined offset: 0 in /homepages/16/d424488600/htdocs/LifeWarriorAcademy/wordpress/wp-includes/plugin.php on line 853

Notice: Undefined offset: 0 in /homepages/16/d424488600/htdocs/LifeWarriorAcademy/wordpress/wp-includes/plugin.php on line 871

Notice: Undefined offset: 0 in /homepages/16/d424488600/htdocs/LifeWarriorAcademy/wordpress/wp-includes/plugin.php on line 853

Notice: Undefined offset: 0 in /homepages/16/d424488600/htdocs/LifeWarriorAcademy/wordpress/wp-includes/plugin.php on line 871

So I’ve changed it back.

I’m afraid that debugging Javascript is beyond me but my hunch is that this isn’t the issue because I can deduct the following:

1) This problem comes up in all 3 main browsers, across different machines and user accounts.
2) I have a subdomain with WordPress installed that isn’t having these issues.

…Does this narrow it down or shed any more light on it?

I think that you’re wrong on Javascript not being the problem. Things like uploading images and inserting photos are all done using Javascript. If they aren’t functioning, something is “breaking” the Javascript for these functions. As this happens in all browsers, that pretty much confirms that there’s a big breaking Javascript conflict somewhere.

The error that you’re getting tells me that there’s a faulty plugin somewhere, or that you haven’t uploaded all of the WordPress files completely, and something is not quite right in there.

If you’ve got this problem in one installation, but not in the subdomain on the same server, that again tells me that there’s something different with this one – and that is 99% of the time a difference in the files that are being used. I know that you said that you did already, but re-upload all of the WordPress files from a new fresh download except the wp-content folder and the wp-config.php file. Also be very careful to look for FTP errors when you do this as they can indicate something going wrong.

Hi, thanks for your help and sorry for the gap in response, I had hired 2 separate people from Fiverr.com to fix this, but they couldn’t. I’m left at where I was.

They both separately tried re-uploading all the WordPress files, but the issue still remains. What else can I do?

They both separately tried re-uploading all the WordPress files, but the issue still remains.

So look at what I said before. Re-uploading the WordPress files will be OK if that was the problem but what if it was a plugin that was causing the issue?

And I do hope that you didn’t pay those others if they couldn’t actually fix your issue….

No I didn’t have to pay them.

I will go through the plugins again one-by-one, I do see that when I set certain plugin induced pages as my homepage, issues such as blank screens in the previews in the backend pop up.

In the meantime, I recontacted my hosting company 1and1, they said they will get back to me in 24-48 hours about if they find anything on their end. They’re shared hosting so I don’t know if that could produce problems, but we’ll see.

I’ll let you know in a bit. Thanks ??

So, one plugin causes my all my preview pages to be blank with the URL:

https://www.website.com/wp-admin/post.php

instead of

https://www.website.com/?preview=true&preview_id=582&preview_nonce=f0ce2c44c7

Another plugin doesn’t upload images within it. This plugin is also installed on a subdomain but with no such problems.

A third plugin just doesn’t load anymore even though the work already done by it, is still there on the front end.

I don’t need the first & third plugins so I’m deactivating them, but I still don’t know whether this is the fault of the plugins or WP or hosting.

The 2nd plugin I need, it works on my subdomain which is confusing.

What do you make of this new information?

Sounds like you have some bad plugins. You need to contact the plugin authors about these issues,

I’m thinking this could be, the first plugin when activated, makes unrelated and unconnected preview pages go like how I described above. I don’t know how a plugin can do that though.

But I’m still scratching my head as to why plugin #2 works on my subdomain. They are both updated to the latest version. I’ll contact them but if it works on my subdomain then I’m thinking it might be something other than the plugin.

But I’m still scratching my head as to why plugin #2 works on my subdomain.

It could be conflicting with another plugin or your theme on the problematic site.

I fairly sure that it works on my theme (same theme on both sites). I also tried activating only that plugin and no other plugins, but the problem remains, so I’m not sure about plugin conflicts.

Unfortunately, the only way to confirm a plugin conflict is to deactivate the lot and start activating them again in pairs – commonly called “the plugin dance”. Also try checking your site’s error logs for messages that might give you some more clues. Your hosts should be able to help you accessing your site’s error logs.

So with 13 plugins, I should test the plugin with the others one-by-one? How would I recognize a conflict if the same fault exists both when it’s the sole activated plugin, and when all the plugins are activated?

My hosting company 1and1 found no error logs when I called them 2 weeks ago.

So with 13 plugins, I should test the plugin with the others one-by-one?

Yes. I thought you had done this already.