I have a problem with my website. In the joomla template I have BluePage Builder. At homepage I've put an HTML tab with iframe code for a youtube video. I have changed the parameters at Global Configuration to No Filtering. I checked Allow IFrame to JCE Editor. My website is kaltsas.gr. It doesn't delete the html code at editor but also it doesn't show it at front end.
Well, besides the point that you should ASAP update your Joomla to 3.6.4 (check the official Anouncement Joomla! 3.6.4 Released and also search JSE for
from the link you provided it seems that Default Menu Item (Homepage) for Greek language DOES NOT have the same module like other two languages (EN and BG) have.
They both have following DIV
<div style="max-width:700px;height:450px;" class="st-youtube ">
<iframe width="700" height="450"
and video is shown correctly, while Greek homepage has only
<p> paragraph with
<img> image tag in it with embed code changed to
data-mce-json, which might be the problem with JCE, I'm not sure, so try updating it too.
It is not possible to say for certain just by looking at frontend and without access to admin, but you should check what is set for other two languages as homepage menu item which is working, and duplicate it for Greek homepage too.