When USPS tracking says Shipment Received Package Acceptance Pending it means that the post office has your package.
However the post office is still processing the packages and may need to weigh it and ensure the proper postage is paid.
If someone drops off a package at USPS and already pays for the postage online then the package has to go through acceptance before it is sent off to the next sorting facility.
Or if you drop off a package at a package drop off box at USPS then the package gets scanned and says package acceptance pending and then it goes on it's way.
If the proper postage has been paid then the package gets sent out to be in transit.
Sometimes a package may be stuck in acceptance pending even though the package has been accepted and is on it's way to you.
When a package through USPS says pending acceptance it could be that the package just has not been fully processed yet.
Or the package did not get an additional scan before it was sent off to a sorting facility.
I have had packages being shipped through USPS that were stuck on pending acceptance for a few days or until the package actually reached me.
It does not mean that your package was not accepted as sometimes USPS employees don't always scan packages like they are supposed to.
Regardless your package is likely still in transit even though the tracking is stuck on pending acceptance.
I would not worry until it's been 5 to 7 days and you haven't received your package.
I've also had USPS packages delivered to my post office and I got the package and yet it still says package acceptance pending.