Podcast cover art must be at least 1400 X 1400 pixel JPG or PNG, in RGB color space, and hosted on a server that allows HTTP head requests.

Your image is the correct dimensions (though there actually isn't any point in its being larger than 1400 x 1400) but the filesize is too large at 729kB - it must be less than 500kB.

A couple of points which don't impinge on the validity of your feed which are worth looking at. Looking at the top episode, the 'itunes:subtitle' tag is very long and will be truncated in display, so it's worth keeping it short.

The 'itunes:summary' tag contains some HTML code - iTunes will not render this but will show the code, which looks messy. You should stick to plain text. The simplest way is to write the summary in TextEdit in plain text mode and paste it in. Don't use a word processor.

There is HTML in the 'itunes:summary' tag for Episode 2.

<itunes:summary>Emirates Diary Podcast - Episode 2 - Termination

In the Emirates Diary Podcast episode, you will hear about Deepak and Thenji discuss about Ministerial Decree 765 which covers Termination of Employment Contract under Limited and Unlimited contract.Experts on the panel of Discussion:&lt;a href=&quot;http://emiratesdiary.com/podcast/edp001-standard-offer-letters-as-per-uae-labour -law-podcast#Aboutthe_Expert" target=&quot;_blank&quot;&gt;Thenji Macanda of Taylor Wessing&lt;/a&gt;

Deepak Machado of Emirates DiaryShow Notes - What is covered in this Episode?Termination of &lt;a href=&quot;http://emiratesdiary.com/uae-labour-law-2/limited-contract" target=&quot;_blank&quot;&gt;Limited Contract&lt;/a&gt; - How can it be terminated?

Terminated of &lt;a href=&quot;http://emiratesdiary.com/job-tips/what-is-an-unlimited-contract-employment-contr act" target=&quot;_blank&quot;&gt;Unlimited Contract&lt;/a&gt; - How can it be terminated?

Compensation when Terminating Limited or Unlimited Contract for employee or employer;

Reduction in Limited Contract Terms;

&lt;a href=&quot;http://emiratesdiary.com/uae-labour-law-2/article-120-termination-10-reasons-ter mination" target=&quot;_blank&quot;&gt;Article 120 - Reasons of termination by Employer&lt;/a&gt;;

&lt;a href=&quot;http://emiratesdiary.com/uae-labour-law-2/what-is-a-notice-period" target=&quot;_blank&quot;&gt;Notice period&lt;/a&gt;;

Reasons for bringing this Decree by MOL;

Ways for companies to retain staff and employees.</itunes:summary>

I would have expected all this to show in iTunes but in fact it looks like this (I have to post an image as I can't copy out):

So perhaps you can get away with it. They may have recently changed the way iTunes handles this.

Your image URL is http://emiratesdiary.com/wp-content/uploads/2016/02/emirates-diary-podcast-lates t-feb.jpg and this does not work, simply producing the notice 'Bad request'.