I bought the Metz expansion - it did not download, I try to download and it gives me a new in-app purchase opportunity, then it tells me I have already purchased it - but not downloaded it -
it just downloaded it - inexplicably - after 10 tries

Well it has not fixed it for me ….

I read this thread with great disappointment - why - because I am having exactly the same problem and it seems to me that "Pip" has exactly the same answer for everyone - useless and "it's your fault." Please post a real solution - not the obvious is IAP purchases enabled.