Check that the internal font name ( displayed when you double click it ) is the same as the filename. If not, you may need to rename it so that the filename matches the internal font name. That ought to work. Pretty sure it used to work anyway. Of course, you'll need to have a license which permits you to redistribute the font.
An easier ( and potentially cheaper ) option may be to make a bitmap font of Vivaldi and use that. You neatly sidestep licensing issues ( since the US copyright office stubbornly refuses to accept that the physical image of a typeface can be copyrighted ) and you won't have problems loading and displaying it. Should be faster too.
Of course, if you're using it as a gadget font, that won't work. But if you're using it as a screen font in a BlitzPlus game, it will.
An easier ( and potentially cheaper ) option may be to make a bitmap font of Vivaldi and use that. You neatly sidestep licensing issues ( since the US copyright office stubbornly refuses to accept that the physical image of a typeface can be copyrighted ) and you won't have problems loading and displaying it. Should be faster too.
Of course, if you're using it as a gadget font, that won't work. But if you're using it as a screen font in a BlitzPlus game, it will.