Accept or pickup?

[organization13_games]

So I shipped out two items yesterday, dropped in the mailbox. All of them said the post office took them, except two, which both say "Accept or Pickup." Does anyone know what this means? Should I be worried or is it something the post office tends to do? 

Also, this is my first question. I wasn't sure what "board" to put it under. 

[*coins]

@organization13_games

You got a good reply from lintbrush here: https://community.ebay.com/t5/Selling/Accept-or-pickup/m-p/27176134#M996164.