The problem was that ! I had "http" adress i wordpress setting, I change it into "https" and now it's OK ! 

Thank you very much !

Fabien.

Please navigate to Dashboard > Settings > Genera Tab and check your website URLs:

If those options are disabled, find them in the root directory wp-config.php file and change to https:// secure protocol.

If all is correct, please check your website root directory .htaccess file.

Also, please doable all security plugins during this testing period.

I see the error on your screenshot appear only when I allow Media Uploading. And there is wpdiscuz in the error, like you can see in my screenshot. I think you must make an update to correct the problem, no ? 

Thank you for your help.

PS: I see the guy with "fix-my-compressor.com" have the same problem (but the topic has disapear).

Here is the screenshot:

Thank you, I will see that. But There is no sreenshot, can you add it please ? 

We've seen the following js error on the console that causes the issue. The reason of the issue, may the wrong server configuration in the .htaccess  file, so please check and make sure everything is correct.

Another probable reason may be the plugin conflict, so please deactivate the plugins one by one and check after each deactivation to find the problem maker one.  Please see the screenshot below: 

You can test here : https://steelbookpro.fr/2020/05/26/le-cinquieme-element-un-steelbook-4k-zavvi/

Before I instal the new Media Uploader, the problem was the same. 

And, strangely, I have no problem on my other site (very similar site) : http://www.4kpro.fr/2020/05/27/larmee-des-morts-une-edition-collector-blu-ray-4k-uk/

But on this second site, I had never instal any add on.

Please leave the example URL to allow us to check it.

Can you help me for this please ?

Thanks.