How can product keys become invalid or expired?

[TinyWiking]

Forum keys (which is what GoG has provided you with) actually has an expiration date. It's not the end of the world as we can credit them manually if you open a ticket (support.paradoxplaza.com). For the older games that didn't provide a key you should ask GoG to request them (as we can't see which games are missing keys) and then they can request them from us.

 

[TinyWiking]

Sadly not, Epic doesn't have a way to distribute keys so there are none for those products. Hopefully in the future they'll create an API similar to what Steam uses so we can read ownership and credit customers directly with their games but that's something we sadly have no control over ><!