PowerPoint, and what it can't do
PowerPoint has a known limit with custom fonts: it doesn't apply the advanced ones. Your letters and your spacing come through. Your kerning, your joins and your versions of a letter don't.
This is true in every version of PowerPoint, on Windows and Mac. It isn't a setting, and it isn't specific to Inkling — PowerPoint doesn't apply this class of font feature at all. Word does. PowerPoint doesn't.
What it looks like
Your handwriting, correct and recognizable, but flatter — every 'e' the same 'e', letters not joining where your hand would join them. On a title slide at a large size, the repetition shows. In small body text, much less so.
What to do instead
Use an image. Your font's page has an ink image export: it draws a short line of your text — up to 80 characters, on one line — as a picture that carries everything, and PowerPoint places it like any other picture. Best for a title or a quote. It's part of Pro.
Or accept the flatter version for small text, where it reads fine.