I also faced the same issue, and I reported it in Change in notetype not synced - AnkiDroid (Android) - Anki Forums (ankiweb.net).
The link to Anki Manual given in the above post didn’t help me resolve the issue (because the steps given there was exactly what I did to change the fonts.)
I ended up resolving it by copying the styling section of my note template from Anki on my laptop, sending it to myself via email and then copying and pasting the same to AnkiDroid on my phone.
Note that the font file was synced as expected but the change in the CSS was not synced.