I can not add fonts to my Onyx Boox Note Air 2 FW 3.5.4

Good morning

Trying to add extra fonts to my Onyx Boox device and it doesn't seem to work.
I download and try with both formats ttf and otf, copy to Fonts folder in the root but nothing shows up on the font selection menu from the reader software.
I tried on epub formated texts.

I try with another reader (Moon+) and the fonts worked on the device

I check on all the tabs (CJK, English & System)... normally they may show up on the system menu doesn't it?)

Thanks