I know this is a while, but in case others are looking for a solution to this ...
In iOS 9 Apple started requiring App Transport Security on URLs. This means that "http:" needs to be replaced by "https:".
When you get an image URL like artworkUrl60 it still comes as "http:" because Apple doesn't want to break existing applications.
The logical thing to do is to replace the "http:" with "https:".
But that doesn't work! It doesn't even work if you paste it into a browser because the mzstatic.com website doesn't appear to have a valid certificate.
The solution is to either completely turn off ATS (not recommended) or to white-list mzstatic.com.
Open Info.plist and insert the following:
<key>NSAppTransportSecurity</key>
<dict>
<key>NSAllowsArbitraryLoads</key>
<false/>
<key>NSExceptionDomains</key>
<dict>
<key>mzstatic.com</key>
<dict>
<!--Include to allow subdomains-->
<key>NSIncludesSubdomains</key>
<true/>
<!--Include to allow HTTP requests-->
<key>NSTemporaryExceptionAllowsInsecureHTTPLoads</key>
<true/>
</dict>
</dict>
</dict>
That appears to fix the problem.
David