Some of the text I’ve highlighted are not showing
Highlights are strictly related to the text you are highlighting.
For example: if you’ve highlighted a part of the Quran in Arabic and then change the font of the Arabic text, the highlights you’ve done on the first font will not be showing anymore.
The same will apply to transliterations and translations
If you’ve highlighted some text in English and then choose another translations (even if it’s another english translations, for example from “Hilali-Kan” to “Saheeh International”), then highlights you’ve done on the first translation will ne bot showing anymore.
If you wish to recover your highlights, you will have to switch back to the original text which you’ve used to do the highlights.