Seems to me a pretty clear case of policy change. A few moths ago it was "We don't know how long it will take to fix, but here's a credit.".. now it's. "we can not offer any form of reimbursement for the purchase."...
This thread is in no way sponsored by Amazon
PS. I would introduce these ... people to Mastercard conflict resolution and whatever consumer protection law applies (which might also influence Kobo policy, where you are buying from...) But that's probably also a good way to get you account nuked, if you still care about that kind of thing.