I picked up some Grandstream material in the last week and my surprise began when I couldn't register the secondary stuff to my Cloud account. It appears that they addressed this issue last year.
https://www.grandstream.com/online-marketplace-warranty-limitations-policy-pageOops. I suppose it's fair, but GS doesn't want any of the product that you can administer in the cloud to be purchased or resold on the secondary market.
Meanwhile, I have a couple of gray systems and 10 or so phones of questionable heritage. :-( Time to figure out a workaround...
Carl
EDIT: After wailing and gnashing of teeth and texting Grandstream, I am now able to log into my cloud account and add this unit to my systems. The seller (Phillips Communications) on Ebay contacted who he bought it from and they released my new system back into the pool. Now it's mine. It's the first time they have had to deal with the 6300 series systems.