I had four Sonos Connect Amps that were eligible for the 30% upgrade credit. These credits have been viewable from my account. Over the past few years, I have been replacing them with Amps from resellers other than Sonos with the intention of accumulating those credits for a larger purchase, such as the Sonos Arc Ultra. 

Today, I attempted to purchase the Arc Ultra through my account and discovered that all 4 previously activated, 30% upgrade credits had been removed. Upon contacting support regarding this issue, they informed me that the devices must be actively registered on my account for upgrade eligibility. As an alternative, they suggested utilizing one of the available 15% offers from my current 18-zone system. This is despite their own website still claiming in faq the following - 

“Can I resell, gift, or donate my product after activating or
using my upgrade credit? Yes. The next registered owner will not be
eligible for the Sonos Upgrade Program.”

It’s been a tough summer & fall with the app, and I’m not sure if I can keep trusting the company to do the right thing. Buyer beware.