does it appear white in the editor and the game, or just the game, or once you place it in the editor it disappears as i have had these issues recently and i believe that it has to do with the texture type, have you for instance changed the texture type manually e.g. trying to apply transparency by changing the texture from .dds to .png because i think that that is the problem i have been having
EDIT: have just tried out my theory and it isn't that and now mine is also broken so i suggest reinstalling
EDIT 2: sorry try this go into the editor settings of the FPSC toolbox and tick the entities export comment setting i think that should fix it, sorry for so many edits
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