Sorry to hear you have problems to unlock RoomWorks SE via registration, and hope iOS 11.0.3 did not break anything.
We will check the issue and get back to you asap.
I just wanted to add that when I registered back in April 2017, I was on an iPad2 with 32-bit version of Cubasis. With iPad 2017 running 64-bit version, maybe this is somehow confusing registration process.
Also, in the iOS ecosystem there is no software pirating as we are all paying users within the App Store. I really don’t know why you added the registration complication if RoomWorks is ultimately free. Be nice to see registration for RoomWorks removed in next version.