Yes. EBay expects sellers to ship within 7 days of cleared payment.
But yes, Paypal Holds those cleared payments for up to 21 days against the new seller's good performance.
These are Buyer Protection policies.
And they are in the information the seller gets from eBay and from Paypal when we make a sale.
Since your seller has informed you that he has not yet shipped, you could contact him and ask for the date and service of shipment, as well as the tracking number of the shipment. (The tracking number is not important... to you anyway.)
If he does not provide this information, go to the Resolution Centre and open an Item Not Received Dispute. The first step is usually to contact the seller, but youhave already done that, so go on to Step Two and escalate to a Claim.
If the seller cannot prove that you have received the shipment, either he refunds you in full, or Paypal will and go after him hard for their money.
BTW, the seller can use the Held payment to purchase shipping labels at a discount through Paypal. There is no excuse for not shipping.