Why Do I Have Missing DLLs in My SystemLink 2025 Installation?

Issue Details

In my SystemLink Server 2025 Q1 or SystemLink Server Q2 installation, the AlarmInstance service and the TagRuleEngine service won't start, and I get errors like this in the log files:

System.IO.FileNotFoundException: Could not load file or assembly 'System.Diagnostics.Debug, Version=4.0.11.0, ... or one of its dependencies. The system cannot find the file specified. ---> System.IO.FileNotFoundException: Could not load file or assembly 'System.Diagnostics.Debug, Version=4.0.0.0, ... or one of its dependencies. The system cannot find the file specified.

Solution

These are the DLLs that are missing in the SystemLink Server 2025 Q1 and SystemLink Server 2025 Q2 installers:

•     C:\Program Files\National Instruments\Shared\Skyline\TagRuleEngine\System.Threading.dll
•     C:\Program Files\National Instruments\Shared\Skyline\AlarmInstance\System.Diagnostic.Debug.dll

You have two options to resolve this issue:

1. Upgrade to SystemLink Server 25.8.0 or later-- these DLLs have been added to all SystemLink Server installers after SystemLink Server 2025 Q2
2. Copy and paste the missing DLLs from other locations where SystemLink 2025 does install them, for example:
    C:\Program Files\National Instruments\Shared\Skyline\TestMonitor\System.Threading.dll
    C:\Program Files\National Instruments\Shared\Skyline\TestMonitor\System.Diagnostics.Debug.dll

Additional Information

SystemLink Server 2025 Q1 included an update to its MongoDB driver, which created the new DLL dependencies.  The resulting missing DLLs issue is expected to occur in both SystemLink Server 2025 Q1 and SystemLink Server 2025 Q2.  However, it has ONLY been reported in SystemLink Server instances which were configured to point to a remote Mongo db instance using the Atlas cloud service.