table of contents problem in epub to azw3

[quizzz]

i took an epub which had a table of contents with only major chapter heading. I expanded it through Auto generating toc in sigil, getting all headings and subheading.

on conversion to mobi and azw3, and then viewing in calibre, all is fine, toc is changed as in edited epub.

Problem:

when i send converted mobi to kindle, it works as expected with full toc.

BUT when i send converted azw3 in kindle, the original toc only is working. it appears as if i have done nothing to my original epub. but when i viewing same azw3 in calibre viewer, full toc is there.

i am frustrated by this.