There are legitimate reasons for the vendor not wanting to give you the tracking details. Under normal circumstances some vendors do not give out tracking details because it can compromise their shipping arrangements, if LE ordered multiple times from a vendor they could then map the tracking updates to try and find their location or gather further information such as CCTV footage from where the orders entered the mail system. However if your order is long over due then they should by rights pass the tracking on so you can see what is going on, you can easily safely check tracking by using a VPN. There is speculation that checking tracking with Tor can flag the shipment leading to a seizure, how much truth there is in that though I don't know, I would always err on the side of caution and not risk it if it is not necessary. Have they checked it? they should at least be able to do that.