This is a known issue with the "Compatibility" graphics setting. The following is from the Inventor 2013 "Read Me" file:
"On the Application Options, Hardware tab, when you select Compatibility, limited functionality sometimes occurs, including missing thumbnails in Appearance and Material editors, on the View tab Texture On/Off does not function, and so on."
Try a different graphics setting and/or make sure your graphics drivers are up to date.
Best regards,
Charles
Thanks Charles
I have 2015 installed too & the thumnails work, it's 2013 where they don't.
Will look to update graphics driver just incase.
Andrew
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