Mobile app font validation

I’m wondering if there is any tool on the internet or an app that check/validate fonts for mobile apps (or for apple only).
I’m facing and issue that a newly exported font file is not loading into a client’s app. The old version of the font seemed to work fine but I needed to remove some features. After the new export it just stopped working.

I read about issue that PUA mapped glyphs caused some problems with iOS 11 but the new font doesn’t have any glyphs in that area of unicode. It only has latin and cyrillic glyphs.

any ideas?

Does it properly install and work in Font Book? (There is an “Validate Font” command when you right click a font in Font Book). I don’t think it has different validation than iOS. If It works on MacOS and not in the app, there might be a different problem.

Thanks, Georg.
Yes, it validates just fine in FontBook. OTMaster doesn’t show me any errors too. Must be a problem on the client’s end then