No font name is specified in the Visualization Properties > Fonts tab.

No font name is specified in the Visualization Properties > Fonts tab.

Consider the below described scenario:

1. The dashboard is opened in the Spotfire Analyst.
2. Right Click on the Visualization. Go the Properties >> Font
3. The 'Font: ' option is blank. 
4. Please refer the below image:
    

This behaviour occurs because the font used in that particular visualization is not installed on the machine. When the analysis is opened in the Spotfire Analyst the required font cannot be found but Spotfire is still able to show the visualization data.  In this case the font used in the visualization needs to be installed on the machine on which the analysis is opened. 

Please refer the below Knowledge Article for more information on the Web Player displaying different font than what is displayed on the Analyst.
https://support.tibco.com/s/article/TIBCO-Spotfire-Web-Player-displays-a-different-font-than-what-was-used-in-the-TIBCO-Spotfire-Analyst How to install or remove a font in Windows
http://support.microsoft.com/kb/314960