What kind of error is iTunes giving you?
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
SoundCloud does allow HTTP head requests. If you are seeing this error message, it means that your cover art is not within iTunes’ requirements. If you want to submit your RSS feed to iTunes, you must make sure that your profile image’s artwork is at least 1400x1400 pixels, and no larger than 3000x3000 pixels.
If your artwork is not between these image requirements, you will receive the error from iTunes that says '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'.
Error .invalid document
Subscriber Redirect field of your Content Settings page, and have broken your RSS feed. Please remove any URL that you have put into this field.
By putting another URL into this section, you will break your RSS feed, and it will no longer work. This field is if you no longer want to use SoundCloud as a hosting provider, and want to redirect your podcast’s subscribers to a different hosting provider.
RSS feed already submitted
If you are receiving this error, it means that you have already submitted the RSS feed to iTunes and is pending their approval. As a hosting platform, SoundCloud has no influence over how long it takes iTunes to accept podcasts. Generally, it can take between 24 hours and 2 weeks for iTunes to accept a podcast.
If you’re still having trouble finding your podcast, try manually subscribing to your own RSS feed. Open iTunes > File > and select 'Subscribe to Podcast.' Enter your RSS feed into the dialog box and click subscribe. After, try submitting your RSS feed to the iTunes store again.
This feed has no episodes
If you are receiving this error, it means that your RSS feed does not have any episodes in it. To learn how to add episodes to your feed, go here.
We had difficulty downloading episodes from your feed
If you receive this error, it’s usually because some of your episodes are not enabled for podcasting. To enable them, head to your tracks' edit page (pencil icon) and select the 'Permissions' tab. Here, check the space where it says 'Include in RSS feed':
To batch approve episodes, head to your Tracks page and select all the episodes you want to have available in your RSS feed. Click the edit tracks button on the top left and select the Permissions option. From there, toggle the option to include in your RSS feed and click 'Save'.