In version 31.000, PDF export may not be possible in certain scenarios in web applications (including the Report Server and Designer). This behavior does not occur on the development PC, but usually only on the end customer’s PC.
The LatestPrerelease service pack is available for List & Label; for .NET, updated 31.0.1 NuGet packages are also available. Alternatively, the folder containing the List & Label modules can be added to the Windows PATH variable (at the same time, you should also ensure that combit.ListLabel31.ConversionToolsExt.x??.dll is present).
A similar LatestPrerelease service pack for the Report Server is expected to be available next week.