When you open your label template or solution in NiceLabel Designer, you receive the error:
The type initializer for 'System.Windows.Media.Fonts' threw an exception
When NiceLabel Automation opens the label file, you see the error in Automation Manager:
No FontFamily element found in FontFamilyCollection that matches current OS or greater: Windows7SP1.
The error message appears only for the first label you open in NiceLabel software. You can open all the subsequent labels in the same NiceLabel session without errors.
The problem occurs if you installed Microsoft .NET Framework 4.7.1 and security updates from January 2018 (KB4055002 or KB4055532).
Microsoft is working on a solution. See this document.
Follow the instructions in this Microsoft article (see Method 1).