Do you have multiple pollers? The way I read your post, you can test the Template and it tests fine. However, when you actually apply it it fails.
1. When you assign the poller are you assigning it with the same credentials you tested or "inherit from node"?
2. I could be wrong, but I am pretty sure Orion tests from your Primary Poller but polls from the assigned poller. Therefore, if you have multiple pollers, try assigning the node to your primary and see if it is an access issue for the additional poller.
