I had the same problem (except only bought Photo v2 for iPad). I tried your method but as the purchase isn't linked to my account it won't restore and I'm back to being a trial user... so basically (I'm not complaining at you BTW) the licence is off in the Ether somewhere and I can't access it. So I would suggest anyone should use the above method with care.
I think the problem is I wasn't in my Affinity account when I purchased it inside the App, so it just put the name I supplied as it being registered to (in v1 I have my e-mail address appearing under the name). However without an e-mail address there's no Affinity account to log into. You'd have thought it could use my Apple account to see the person owning the iPad had bought the product.