The message is generated because CIBSE weather files are not freely provided by DesignBuilder like other weather files. They must be purchased and then copied to DesignBuilder's weather folder.

DesignBuilder has partnered with CIBSE to provide their official UK hourly weather data from our website CIBSE Weather Data Sets page.

If buying the file is not an option then you should use a weather file from the nearest location provided by DesignBuilder or obtain a file from another source.

See also:

Where can I get hourly weather data for my location 

Updated:14.03.2019