Scan fails in Plesk WP Toolkit: This does not seem to be a WordPress installation

Symptoms

• Scan fails in WP Toolkit with one of these error messages:

  PLESK_ERROR: Scanning for WordPress websites was performed with errors:
  Subscription "example.com": Failed to reset cache for the instance #34: Error: This does not seem to be a WordPress installation. Pass --path=`path/to/wordpress` or run `wp core download`.

  PLESK_ERROR: Scanning for WordPress websites was performed with errors:
  Subscription "example.com": Failed to reset cache for the instance #34: filemng: Failed to change directory to /var/www/vhosts/example.com.com/wordpress_installation: No such file or directory

• When accessing WordPress tab of domain's card, the following error message shows up:

  PLESK_INFO: Invalid argument not valid semver (" received)

Cause

The WordPress installation has been removed from the website, but the information about this installation still exists in WP Toolkit database.

Resolution

1. Log in to Plesk.
2. Open WordPress from the left panel.
3. Find the non-existent installation using its domain name.
4. Click on the three vertical dots in the upper right corner.
5. Click Detach.

If the solution above does not help, remove the installation from the WP Toolkit database:

1. Connect to your Plesk server via SSH.

2. Create a backup file of the wp-toolkit.sqlite3 database:

   # cp /usr/local/psa/var/modules/wp-toolkit/wp-toolkit.sqlite3 /usr/local/psa/var/modules/wp-toolkit/wp-toolkit.sqlite3.bak

3. Access the WP Toolkit database:

   # sqlite3 /usr/local/psa/var/modules/wp-toolkit/wp-toolkit.sqlite3

4. Remove the orphaned records using the instance ID from the error message which appears during the WordPress scan:

   MYSQL_LIN: sqlite> .headers on

   MYSQL_LIN: sqlite> delete from instanceProperties where instanceId = 34;

   MYSQL_LIN: sqlite> delete from instances where instances.id = 34;

   MYSQL_LIN: sqlite> .quit