I have an iPad 1 and an iPhone 6+. The iPad 1 has (old) Omnigraffle for iOS on it. I cannot download the new OmniGraffle for iOS onto the iPad 1 because it requires an iOS version higher than I can install on that device. I cannot download the old OmniGraffle for the iPhone 6+ because it isn’t available. How do I get my ‘free’ upgrade to Pro on my iPhone 6+?