No Ads: This app is not receiving ads. Your iAd Network Contract has expired. It must be renewed for this app to start receiving ads iAds stopped being served in my apps and I just got the dreaded "No Ads: This app is not receiving ads. Your iAd Network Contract has expired. It must be renewed for this app to start receiving ads" message.

No clear way to do this - the contract has vanished from the Dev connect portal.
I just followed up with Apple Dev Support so YOU don't have to :) 

Answer: even though iAd isn't being officially mothballed until the end of June, Apple is not renewing iAd accounts should they lapse before then.  In my case, my Developer Connect contract ended in Feb and was promptly renewed, but without a renewed iAd contract, and no way to renew it.  Time to look for iAd alternatives if you count on ad revenue as part of your app income.