I just tried and was able to get an OAuth token for the sandbox and
use it to make a private call.
Are you using the sandbox to request the tokens themselves?
http://openapi.etsy.com/v2/sandbox/oauth/request_token
http://openapi.etsy.com/v2/sandbox/oauth/access_token
vs
http://openapi.etsy.com/v2/oauth/request_token
http://openapi.etsy.com/v2/oauth/access_token
We may need to make this a little clearer in the docs.
JKS
--
Justin Kerr Sheckler
Developer API Lead
Etsy.com
jus...@etsy.com