This is really a question for the Type & Typography community. This community is for the Adobe Fonts cloud service which does not deal with fonts licensed otherwise.
None the less, most likely the problem is that if “years ago” is more than 15 to 18 years ago, you most likely licensed (you bought a license to use a font, not the font itself) the Type 1 version of the font. The Type 1 font format, although still supported by Adobe applications, PostScript, PDF, etc., has effectively been surplanted by the OpenType CFF format. Regrettably, some software vendors, such as Microsoft, discontinued support for Type 1 fonts effective with Office 2013 on Windows. Your only solution would be to license either an OpenType CFF or OpenType TrueType version of Serpentine. Adobe no longer licenses Serpentine except via the Font Folio product. You can license Serpentine via Monotype at fonts.com at https://www.fonts.com/font/image-club/serpentine.
- Dov