Customer payment returned to them saying PayPal returns payment if not accepted in 30 days

[Meshelle40]

Why does this happen and what am I supposed to do to accept payment.   This was for an invoice I sent and customer paid

PayPal returns payments that have not been accepted within 30 days of being sent

has happened twice now. Never had this before.  My customers payments are being returned to them. And I get an email saying 

PayPal returns payments that have not been accepted within 30 days of being sent

[AnnaBirkett79]

I’ve had this too and it’s never happened before. It’s automatically stayed on my PayPal balance. I can’t seem to see a way of ‘accepting’ any payments either. Can anyone else help with this?