We enter USPS tracking numbers with each transaction for our customers. When my customer service reps click on the tracking number when helping a customer, the get a "Tracking information is currently not available" message (our customer do too when loggin into their account). However, when we enter the tracking number directly into USPS website, it works fine.
Any ideas how to fix this?
I ran into this issue, and fixed it by setting up an API account with USPS. I didn't do that initially, because I wasnt using their API for rates, but it appears you need the account for getting tracking information as well.
You will get an email with a user id and password. Then place that information in the Magento shipping config -- System -> Configuration -> Sales -> Shipping Methods -> USPS
Check and see if my shipment tracking plugin works for you!