I never gotten that before, Is there a reason?

it also says excess/duplicate account? What does that mean, anyone?

The system probably figured out that you had a previous account and took back your 2 free credits for opening a new account.

I deleted that account and had it closed over 3 years ago.

It still means when you rejoined you shouldn't have gotten 2 free credits.  The 2 free credits is for brand new members only and not for returning members.  This is to prevent people from closing their account and reopening a new one just to get the free credits.  You would have gotten the free credits (probably still 3 at the time) when you opened the 1st account. 

I'm not saying you personally would try to scam PBS. But I'm sure there are people who join, post 10 bogus books, spend their 2 free credits and then ignore any book requests they get.  Or close their accounts and reopen one a bit later hoping PBS will have forgotten them.

Here is how the 2 free start up credits work:

We offer members 2 "startup" (free) credits for posting their first 10 books. 

• These credits allow a member to begin ordering books immediately, without having to wait for a request from another member.
• This is our way of welcoming you to the club.
• After the first 2 "startup" credits, you earn credits by sending out books to other members.
• The startup credits are limited to one account per household.

Since you yourself received start up credits in the past, your new account was clearly ineligible to receive them, so they have just removed those from your credit balance.