Why did Jounce swap my font?

Your brand is fine, and the swap is on purpose. When a scan swaps a font, the Start from your website card says so:

Jounce doesn’t have some of your site’s fonts yet, so it used the closest (Gotham → Inter). Pick another below.

The first name in the brackets is your site’s font, and the second is the one Jounce picked. Nothing is kept until you select Save kit, so you can pick another first.

Here is how it picks:

• A font on the list is used as it is.
• A serif font that isn’t on the list becomes Playfair Display for headings and Georgia for body text.
• A sans-serif font becomes Inter for headings and Helvetica for body text.
• A monospace font becomes JetBrains Mono for headings and Helvetica for body text.
• When your site doesn’t say which kind a font is, Jounce treats it as sans-serif.
• Body font lists only the fonts that show reliably in email. A font that’s only on the Heading font list is swapped for body text.

When the scan finds no font for headings or body text, that font stays as it was.

To choose differently, open Heading font or Body font on the Fonts card and pick another. Each name is drawn in its own face, and you can type to search the list. Then select Save kit. See Choose your brand fonts.