I have an older document that used ITC Slimbach which I still have on my computer. Even though the font is open in Font Book (Mac font handling app) when I open the document, it shows all the text in red boxes.
On opening, TypeKit says the font can not be found or will it let me find and change the font. When I try to find the font in the font list within InDesign, the font shows in brackets as [ITC Slimbach] and will not change in the document. I can not even get that font to work as a new text entry in that same document.. I can change the red box text that is to be Slimbach can be changed to another font.
I can use Slimbach in a new document with no problems..