I mailed a book with tracking on December 16th, for some reason it never showed up through pbs. If I go to usps and check it there it shows it was delivered on December 21st.  The person has never marked it as being received. If she doesn't mark it received will I lose my credit????? I did send her a pm asking her to please marked it as received but nothing yet

Did you use PBS DC?  If you used regular USPS DC without going through PBS then you won't get your credit until the recipient marks it as received.

Is it a PBS DC? If it is, send the info from the USPS site to the Team using Feedback and they will get it in the system. If you did not use PBS DC, if they do not mark it received you will not get credit.

Delivery scans do not mean delivered correctly so they will not assume the member has the book and take the credit from them to give to you.

I did use pbs dc, It states that the book had to be picked up from the p.o. after they tried to deliver it.

Many people are or have been traveling, it's possible your recipient is not home yet. If I use non-PBS d/c, I usually wait about 8 - 10 days after it shows "delivered" and then send them the info and ask them to check with their local p.o. as it appears there is a problem. I don't want to wait until it is almost declared "lost" because earlier, the p.o. has a better chance of the carrier remembering, or locating the book.

Once you've received the credit (when the label was scanned) PBS won't take it away from you :)

I'm not totally familiar with all the USPS scans, but it appears to me a orange card was left and later that day the addressee (or official agent) picked up the package a few hours later.  Other than a signature delivery, this one looks more 'guaranteed' than say just delivering to a mailbox.

OTOH, if you used PBS DC your credit has been received and will not be removed from your account!  I'd wait another week, then probably forward a copy of the USPS scans to PBS Admin.