I'm trying to get an OAuth token for the sandbox site. I can sign in to the sandbox and click the "I agree" button on the "Grant Application Access" page but it doesn't redirect back to my application. Instead it takes me back to the login page. Logging in again redirects me to https://pages.sandbox.ebay.com/messages/page_not_responding.html?RlogId=t6ldsskrce.%60hqilqq6brqfsjej%3F%3Ckuvifvqnpfg%2Buriva.qctp5654-1796a4df0ee-0x13d
I've tried it on the live site using the same URL (with .sandbox removed) and it works fine.
It doesn't matter if I follow the link from my application or if I click the test signin button in developer tools, I get the same result.