Also, I've found this unresolved issue about the Sell link not working.
It is from 2018 and it's quite surprising that it hasn't been resolved
for 5 years. Do people just not use the selling UI in the sandbox?
I'm experiencing both of the issues that you are describing. Problem 1)
is the real blocker as accessing any selling-related functionality in
the Sandbox UI NEVER succeeds. Also tried this suggestion to use the
ValidateTestUserRegistration but it did...
I can log in with users created via this form but if I click on the
selling URLs:(A)
https://bulksell.sandbox.ebay.com/ws/eBayISAPI.dll?SingleList&sellingMode=AddItem
(B)
https://www.sandbox.ebay.com/mys/home?CurrentPage=MyeBayAllSelling&ssPageName=S...
