Unable to login to WordPress admin dashboard using Plesk preview: Cookies are blocked or not supported by your browser

Symptoms

• When trying to login to WordPress admin dashboard, the following error is shown:

  ERROR: Cookies are blocked or not supported by your browser. You must enable cookies to use WordPress.

• Website Preview is set to Default Quick Preview in Tools & Settings > Website Preview:
  
  

Cause

Bug #PPPM-11633 in Plesk which will be fixed in one of the future releases.

Resolution

As a workaround for Plesk Obsidian:

1. Connect to the server via SSH and disable Plesk access on port 443

   # plesk bin admin --disable-access-domain

2. Log into Plesk.

3. Go to Domains > example.com and click Preview.
   

4. In the new window, add https in front of the link in the address bar:

   https://203.0.113.2/plesk-site-preview/example.com/https/203.0.113.2/wp-admin/

Note: if the solution above does not work make sure that Domains > example.com > Databases > phpmyadmin > prefix_options > siteurl and home are not customized. Correct values should be https://www.example.com for both

Note: For Plesk Onyx there is no workaround available at the moment. Consider using a local hosts file to access CMS that is not publicly available or upgrade Plesk to Obsidian to use the workaround from this article until the fix becomes available.