Unable to log in to the WP Admin dashboard by using WP Toolkit: JSON: Illegal Token

Symptoms

• Unable to log in to the WP Admin dashboard by using WP Toolkit at Domains > example.com > WordPress tab > Log In button:

  An error has occurred when decoding JSON by Zend_Json: Illegal Token

• Same error is displayed in during the following operations as well:
  Domains > example.com > WordPress > Updates > Check for updates
  Domains > example.com > WordPress > Clone

• The following log is found in at /var/log/plesk/panel.log with Debug enabled:

  DEBUG [util_exec] Finished in 0.6062s, Error code: 0, stdout: "https://www.example.com/wp-login.php"
  PHP: [notice X 0][/var/www/vhosts/example.com/httpdocs/wp-content/plugins/elementor-pro/modules/loop-builder/module.php::200] strpos(): Passing null to parameter #1 ($haystack) of type string is deprecated [array (
  'trace' => '
  0: ElementorCoreLoggerManager -> shutdown()
  ',
  )]

  [extension/wp-toolkit] An error has occurred when decoding JSON by json_decode: Syntax error
  JSON: "https://example.com/wp-login.php"
  PHP: 2023-09-19 13:36:23 [notice X 0][/var/www/vhosts/example.com/httpdocs/wp-content/plugins/elementor-pro/core/editor/editor.php::118] Using ${var} in strings is deprecated, use {$var} instead [array (
  'trace' => '
  #0: ElementorCoreLoggerManager -> shutdown()
  ',
  )]

• Logging into WordPress Admin Dashboard is working as expected using the native WordPress login functionality, e.g. https://example.com/wp-admin

• Website is using PHP 8.x version

Cause

Elementor plugin bug.

Resolution

Contact Elementor plugin Support to address this issue.

While the issue is not fixed by the vendor, here are some possible workarounds:

• Switch the website to an older PHP version (e.g PHP 7.x)
• Login to WordPress through the Subscriptions Screen (using the Active List rather than Dynamic List view