In SkySafari 6 Pro, all the in-app purchases except for the H-R diagram fail to download. This is probably due to failure to play nicely with Apple's iCloud storage. I have 2Tb of iCloud storage. Apple shows the iCloud storage for the phone (iPhone 13 mini, iOS 17.0.2) as 397.1 Gb of 2 Tb. The iPhone's physical storage is 256 Gb. I have not been able to download the in-app purchases since I increased my iCloud account from 200 Gb to 2 Tb. I have no idea how much free local, physical storage the phone has because Apple hides that inside the total for iCloud storage.
Apple doesn't give me a way to delete iCloud storage items just from the phone and not from the cloud -- the only option is to "delete from iCloud". I need access to everything I have in iCloud from my MacBook, so "delete from iCloud" isn't an option. On the MacBook I have the choice of whether to delete a file from local download or from iCloud, but there doesn't seem to be any way to choose that from the iPhone: it's all in the cloud and supposedly "just works".
I probably won't upgrade to SkySafari 7 unless this bug is fixed in 7.