Some letters are missing
You type a character and get a blank, a box, or a letter from another font. Three causes.
1. You haven't written it yet
Most likely. A font contains only what you've put in your hand. The Letters room shows everything you've written and what's still missing — anything not yet written won't be in the font.
Fix: write the missing ones, then remake the font. Adding letters to an existing font takes seconds and doesn't disturb what's already there.
2. It's beyond what your tier builds
Everyday letters, numbers and common punctuation are included at every tier. Accented letters, currency signs, and less common marks are part of a wider set that Pro builds.
Here's the part worth knowing: you can write them at any tier, and we keep them. They're held out of a Free font rather than thrown away. Upgrade and remake, and they appear — no rewriting.
See How much of your hand and Free and Pro.
3. It's not a character we support
Inkling covers the Latin alphabet, numbers, punctuation and common accents. It doesn't currently cover other writing systems — Greek, Cyrillic, Chinese, Japanese, Korean, Arabic, Hebrew — or emoji. When one of those is typed, your computer substitutes another font.
Working out which
Open the Letters room. If the character is listed as missing, it's cause 1 — write it. If it's shown as written but marked as needing Pro, it's cause 2. If it isn't listed at all, it's cause 3.
A note on spaces
The space character is always present and doesn't need writing.