So I sold an ergo infant insert on ebay 1 week ago. I promptly sent an invoice and told them I required payment within 3 days or otherwise contact me and let me know when they could pay.

It has now been a week and still no contact at all.
I had a look at the feedback and most were good but one said NO CONTACT/ NO PAYMENT. Now I am unsure of how serious that buyer is.

Should I send another message and how long should i wait for them to reply? Can I give a second chance if I get no reply?
I really need the money and I had a lot of bids for it.