MS Dynamics SL - System Database is not available in the Find Database screen (98.000.01)

This is happening after upgrading from Dynamics SL 2011 to Dynamics SL 2015.

The issue was caused by the database not being marked as 'TRUSTWORTHY' in SYS.DATABASES (Master Database).

Ran the following statement to correct the issue (replace SYSDBNAME with the name of your 'missing' database).

ALTER DATABASE SYSDBNAME SET TRUSTWORTHY ON;