Not allowed to preview drafts with plugin

Hi!

My problem is this : Whenever I press the Preview button on a draft post, I’m greeted with “sorry you are not allowed to preview drafts” or something similar (the site is in french). Clicking on the permalink in the edit post screen works and clicking on the preview link when viewing the all posts list also works.

Here’s what I’ve tried :
Disabling Public Post Preview (it worked, but we’d rather keep it)
Manually removing “&preview_nonce=3489aed21f” from the url : worked
Checked WordPress Address (URL) : https://mamancafeine.com/wp
Checked Site Address (URL) : https://mamancafeine.com
Checked .htaccess : non-existent since we use nginx
Saved permalinks : No luck

I’ve tried to reproduce in my local dev environment to no avail; everything works fine in local.

I should note that on the production site, the default language is in french, but I’ve set my user to english. The error I get is in french, therefore I think I can safely assume that I am not logged in when following the link.

I think I should also note that my account has the administrator role.

Any help or ideas are welcome!

The page I need help with: [log in to see the link]