I'm having the same issue. I paid $20 for the "bundle", which came with coupons, but I'm having the same issue. The coupons start with G3. Also, the Music Maker doesn't seem to have a serial number, so I think I got the free version.
Assuming you are saying that you cannot enter the codes after selecting items in the Store tab of whichever Magix program(s) you have, problems with coupon codes can really only be resolved by contacting Magix sales, via the Support link in the header of any forum page.
@Russell-Alexander if you have not been asked to enter a serial number to register and validate your version of MM then yes, I think you are correct and you have the free version of the software. What was actually stated in the "bundle" offer?
In the bundle offer, it said "Music Maker Incl. Coupon", and under highlights it said "full version". It didn't mention that it was free normally. But it's ok, I use Sonar Platinum anyway - I just wanted another program to use for quick stuff. I noticed in the original bundle offer, it says "includes vouchers to be used in the Magix App Store", so I'll try that instead of going through the program. I've seen posts about issues with that, as well as workarounds, so hopefully I'll get it all resolved.
Ok, this is ridiculous. The program says the coupons I got are a "value code". I tried to purchase from Producer Planet, then (just to see) and upgrade from the free version of Music Maker to the Pro. NOWHERE did I see any place to enter the codes. I sure as heck wasn't going to "complete the purchase" for the full price of either site.
Are these codes any good, or is it just a come on? Getting a bit ticked off here. "it's not a COUPON, um, it's value code. No, you can't use it here, you have to use it at checkout. Well, no, you can't use it at checkout until you've given us permission to charge your card and agreed to confirm the purchase".