FYI, Fedex, UPS, and DHL do not deliver to all addresses. They all make daily stops at post offices around the country. They have learned to reduce their work load by drop shipping to USPS delivery offices, and pay a minor fee for that last mile deliver by the PO. That may not be the issue for you and RA, but it's a practice that is growing. DHL began it when they ended all service to the USA other than large business deliveries.
There was a Christmas about 5-7 years ago when a huge online season resulted in UPS and Fedex being unable to deliver all of the packages they received just before Christmas. From then on, they have learned to gauge their shipping load, and divert anything they cannot handle, to the USPS.
So the USPS handles a bunch of packages every day that come from UPS and Fedex. Look at the parcels you receive, every one. Notice those from the USPS will often have shipping labels on them from UPS or Fedex also. Those were drop shipped to your local PO most likely.
I comment here because a new issue has begun, Amazon has now created a large shipping network too. I believe it began this past Fall fully. They now ship a large amount of the parcels from various sellers, through private contractors, truckers etc. I don't know any details, but watch your tracking information. It's almost happening enough now, that most don't get received by the USPS until the day before they arrive.
I had that happen to me at Christmas this past year. I bought something on eBay and the tracking showed it shipped the next day, and Amazon was the shipping partner. The item got to Nashville by the 3rd day(Dec 27th), but never left there ever. There was a bomb set off in Nashville on Christmas, so most likely the Amazon shipping facility was affected. The tracking number was a USPS #, as normal it showed as shipped, but never received by the USPS.
So watch your tracking information, that's your best knowledge to figure out what's going on. Good luck,