Unable to change login settings of WordPress instance: Cannot read property 'login' of undefined

Symptoms

• Unable to change login settings in Domains > example.com > WordPress instance > Setup:

  PLESK_INFO: Something went wrong.
  r is underfined

  or

  PLESK_INFO: Something went wrong.
  Cannot read property 'login' of undefined

  or

  PLESK_ERROR: Administrator account not found for this WordPress instance. Please create administrator account manually in WordPress

• Opening http://example.com/wp-admin.php redirects to http://example.com or shows the error below:

  PLESK_INFO: Sorry, you are not allowed to access this page.

• There is no "Administrator" user for the instance:

  # plesk ext wp-toolkit --wp-cli -instance-id 1 -- user list --format=json --quiet --role=administrator

  Note: instance-id can be seen in the address bar of a browser by opening the instance in Domains > example.com > WordPress instance:
  

• In Domains > example.com > WordPress instance > Database > open in phpMyAdmin > example_usermeta there are no records with meta_key example_capabilities and example_user_level for user_id 1:
  

Cause

Corrupted WordPress instance database.

Resolution

1. Log into Plesk.

2. Open Domains > example.com > WordPress instance > Database > necessary database > open in phpMyAdmin > example_usermeta.

3. Click Insert button:
   

4. Type the following:

   First query:

   CONFIG_TEXT: user_id - 1
   meta_key - example_capabilities
   meta_value - a:1:{s:13:"administrator";b:1;}

   

   The second query:

   CONFIG_TEXT: user_id - 1
   meta_key - example_user_level
   meta_value - 10

   

5. Click Go:
   

Note: If the table does not exist, the last backup should be restored or Wordpress Support Contacted, to further assistance to reacreate the table.