I'm sorry for that. The reason you get the "page not found" is the topic is private.

However, see the reason of the issue below: 

Your website URL is wrongly configured with http:// unsecure protocol. This should be changed to https:// , because you're currently use https:// in website:

Please edit the wp-config.php file of your WordPress and change the URLs from unsecure http://protocol to https:// protocol.

Here are the incorrect lines in your wp-config.php file:

This will fix all your future problems. This is not only the wpDiscuz issue, you'll always have lots of problems with all plugins which work on AJAX.

First of all, the media is not uploading. If you select an image, then there is a sign that it is "uploading" but when we post the comment, the image doesn't show.

Please follow this support topic: https://gvectors.com/forum/media-uploader/installation-of-up-loader-exactly-the-same-as-my-other-site-but-on-fix-my-compressor-com-it-doesnt-work/paged/2/#post-23574

Moreover, users can send comments without any text. 

This is the known issue, and it will be fixed in the next version update.

Also, the rating system isn't always working. Our clients cannot rate the post, and a lot of them are writing to us about that. Help us solve the issue as soon as possible.

We've just checked and don't find such an issue. Please specify what exactly doesn't work.

We had an issue with your plugin. After the update to wpDiscuz 7.0, we've had problems. First of all, the media is not uploading. If you select an image, then there is a sign that it is "uploading" but when we post the comment, the image doesn't show. Moreover, users can send comments without any text. This is not right, and it wasn't like that before. Also, the rating system isn't always working. Our clients cannot rate the post, and a lot of them are writing to us about that. Help us solve the issue as soon as possible.

Our website is littercon.com