Error while opening Applications tab: ERROR: Call to a member function getWordPress() on null (Instances.php:152)

Symptoms

1. The following error message is shown on an attempt to enter Domains > example.com > Applications:

ERROR: Call to a member function getWordPress() on null (Instances.php:152)

2. The following SQL query can be found with enabled debug (SQL queries) in /var/log/plesk/panel.log:

[2017-06-01 10:38:26] DEBUG [dbquery] [135] SQL: SELECT `smb_apsInstances`.* FROM `smb_apsInstances` AS `smb_apsInstances` WHERE (`registryResourceId` = '0b52b2e3-f878-4535-aa39-f422e47df05d')
[2017-06-01 10:38:26] DEBUG [dbquery] [135] END: 0.00022602081298828 sec
[01-Jun-2017 10:38:26 Europe/Berlin] PHP Fatal error: Call to a member function getWordPress() on null in /usr/local/psa/admin/plib/Smb/View/List/App/Instances.php on line 152

3. registryResourceId from the query in step 2. is missing in the table smb_apsInstances :

# plesk db "select * from smb_apsInstances where 'registryResourceId' = '0b52b2e3-f878-4535-aa39-f422e47df05d';"
Empty set (0.00 sec)

Cause

Database inconsistency.

Resolution

1. Create a backup of psa and apsc databases :

# mysqldump psa -uadmin -p`cat /etc/psa/.psa.shadow` > psa_current.sql

# mysqldump apsc -uadmin -p`cat /etc/psa/.psa.shadow` > apsc_current.sqll

2. Check that registryResourceId exists in apsc database:

# plesk db
mysql> select * from apsc.aps_registry_object where uid='0b52b2e3-f878-4535-aa39-f422e47df05d';
+----+--------------------------------------+--------------+---------------------+---------+
| id | uid                                  | type         | creation_time       | enabled |
+----+--------------------------------------+--------------+---------------------+---------+
| 8  | d0dc710a-74ec-4fb2-8b5f-d2b7ccb1de00 | aps.resource | 2017-05-29 23:45:10 | y       |
+----+--------------------------------------+--------------+---------------------+---------+

If this query returns empty set then please refer to the following article:
APSC inconsistency: Cannot find registry resource for Application ID

3. Check that affected domain is presented in apsContexts table:

mysql> select id from domains where name='example.com';

+----+
| id |
+----+
| 1  |

mysql> select * from psa.apsContexts where pleskId=1;

+----+-----------+---------+-------+----------------+
| id | pleskType | pleskId | ssl   | subscriptionId |
+----+-----------+---------+-------+----------------+
| 1  | hosting   | 1       | false | 3              |

4. Find all required values to insert:

mysql> select id from smb_apsPackages where vendor like '%WordPress%';

+----+
| id |
+----+
| 2  |  
+----+

mysql> select id as parentContextID from smb_apsContexts where packageId=2 and contextType=0;
+-----------------+
| parentContextID |
+-----------------+
| 3               |

mysql> select id as ContextID from smb_apsContexts where packageId=2 and contextType=1;

+-----------+
| ContextID |
+-----------+
| 4         |

mysql> select id as metaID from smb_apsMetas where serviceId like '%wordpress%'; 
+--------+
| metaID |
+--------+
| 2   |

5. Get registryResourceId from the error message and insert correct value into smb_apsInstances:

mysql> insert into smb_apsInstances (parentContextId,contextId,metaId,registryResourceId) values (3,2,2,'0b52b2e3-f878-4535-aa39-f422e47df05d');