Custom Fields Plugin – Can't Add New Content

I’m having some issues adding new content to this website. Here is what is going on.

1) I can’t add media images to the website. It gives me an error when I try to upload any images to the site.

2) I can’t add items to a page. I can edit content that is existing, but when I create new content on the page, it won’t show up on the live site.

Here is what I’ve tried so far:

– Disabling all plugins.
– Clearing my browser cache.
– Waiting for a long period of time in case the server was being slow. (which wouldn’t make sense if I can edit existing content)

We are editing this website for a client, so we had no hand in it’s original creation. We can go in and edit/add footer items in the backend. But the builder (custom fields) is not being friendly.

They also use a plugin called “W3 Total Cache”. I thought that may have a hand in this, but even after disabling it, it still doesn’t help.

The website is https://www.sound-craft.com

Any ideas?

Thanks!