Hi @Lara_M,
TinyMCE strips out most tags that wouldn’t be used as part of the options that are part of TinyMCE. You can see an explanation of this here: Adding images to announcements in OJS 3.3 - Tiny MCE - #4 by rcgillis - the same principle applies - if you’ve added additional HTML, it would likely be stripped out.
-Roger
PKP Team