Having serious issue on our game, after we updated it two days ago on 7th February. One of the eight IAP's seems to always fail on all Apple devices. It gives two different errors: "There was an error in transactions: Unknown." and/or "This item is no longer available.". We have reports that some other IAPs fail too, but apparently not always.
Nothing has changed on our end in the IAPs for the past 6 months and the same IAP's are fine on Google and Steam (cross-platform game). So something must have changed at Apples end between our January update and the update two days ago. Reported the problem to Apple yesterday, but it can take days or weeks for them to get back to you.
I now disabled the IAP in question from iTunes, don't want our customers to try and pay for something that gives error or even takes the money but does not deliver the IAP.