A problem with podcast image

Hope you can help me with my question:

I produce podcast on iTunes for several years, but for the last 3 months I have the problem with the podcast picture on iTunes Store:

http://paulvinitsky.com/podcast/podcast2.xml - that's my feed.
I use big pic of 2400x2400 size.

All's working when I see the podcasts downloaded in my iTunes, but when I open podcast page on iTunes Store:

https://itunes.apple.com/us/podcast/trance-dance-show-podcast/id312966881

there's no image....

Read dozens of forums, but didn't find why such problem could arise 😟