Don't always blame the USPS when the shipper prints/enters a shipping label but fails to ship in a timely manner.
Also, if you chose the cheap rate for parcel post or first class vs. priority, there is a huge difference in arrival time. Priority (and many times but not always first class) will take 2 days sometimes 3. Parcel post will take two weeks or more and often times the label won't be scanned again. Parcel post is like media mail...they get tossed in a bin, and that bin does not move again until full.