Help! Huge problem with paypal

I have a disaster! Lol
We'll i decided to sell some item first time and the PayPal.... Already have An account with paypal I use it all the time to buy stuff off eBay but I sold an item and the buyer paid by pay pal on Friday I assume so by clicking " pay by pay pal" anyways no payment has shown up in the account! Nothing In the transactions... Yet when I look up old transactions you can see where I have bought stuff..

Buyer emailed me and said the link didn't match up and the money didn't go through.. However I have another buyer who's said she did pay and it's gone through but nothing in my account? I usually as a buyer pay by credit card thru the PayPal no problems

Why is the payment from the buyer not showing and where has it gone? Is there anything else I need to set up that I didn't?
I really don't need the buyer to give me neg feedback because of pay pal problems TIA