If you have enabled ‘Easy-Read Font on All Fields', this will cause your Markdown syntax to be ignored when displaying your notes.
To disable this setting on iPhone and iPad:
- Unlock your database
- Tap the Database Settings icon (the icon with three sliders in the top left of the screen)
- Tap Customise View
- Scroll down to the Details View section and turn off 'Easy-Read Font on All Fields'