Troubleshooting kfx book- but NO BOLD. NO FONT change option

[erbtui]

hi there,
I am very new to this forum, so hopefully ill get some help

I have an issue (reapiaring rarely) that a book I bought- sent to the kindle as a KFX file format, yet no options to change to the font I have on the device (not even the default bookerly) and no bold option (the slider is gray and won't click).
From what Ive seen on very few posts here (2 years ago on reddit and one here from 2012)- the solution was to convert the book into AZW3/ KFX, and by default it should reappear, but for some reason it doesnt work for me.
But the book IS in kfx format... so I dont know what to do. Its an access accessibility matter for me.
I had convert the book into epub, then the epub to azw3- nothing help in all formats.
Ive also seen that its something to do with the css- I dont know. The book I have this issue is the forth book in a series, yet all three previos books were fine and only this one has no bold option.
Maybe this is a publisher restriction, because even if I literaly copy-paste the whole css from one of the previos books into this one- the layout and everything else work perfectly, yet the font and bold are unavailable to change.
Looking for possible solutions.
Thanks

[texasnightowl]

I had a book recently where I could not change font types. What worked for me on this particular book was when doing the conversion, I think I was doing epub to azw3, on the Look & Feel > "Styling" tab, there is an option at the bottom to "Select what style information you want completely removed:". Put a check in the "Fonts" box.

So, try it?

edit: I'm assuming you are using calibre?

[jackm8]

Can you change font size?