Generic reader doesn't recognize codes

[Hoods7070]

Hi - I have posted this question in various forms in other forums, but am hoping someone can answer it here. My problem is NOT CSS or book structure, it's an ereader issue. (I initially thought it was a problem with the reader being touchy about Calibre codes, but it's not that at all.)

For some reason my generic ereader (JXD A21) absolutely refuses to read CSS. I have emailed JXD "support" to no avail (surprise, surprise!) and can't find a firmware upgrade anywhere - maybe because it's a relatively new reader. It was not that cheap at $130 vs. say, entry level Kindles, and in every other way it does everything I want beautifully, including navigating books etc. So, trading "up" to a Kindle or similar isn't anything I want or need to do. I would like to crack the mystery of the formatting, though, if anyone can help.

I did eventually manage to get paragraph indents by setting these using Word-style indents set (with the ruler) but any CSS (bold, center, paragraph spaces etc. etc.) definitions are totally ignored. I have tried fooling it by using Word-style formatting throughout, but it ignores that too - other than the indents. Pretty weird. Indents were the most important thing I wanted to achieve, so my converted ebooks are now more than readable, but it bugs me senseless that I can't figure out how to get other formatting recognized.

Ideas, anyone?