The customer has bought two items a few days apart.

The second item was a counter offer by me which he accepted.

I then sent a combined purchase order including payment details and am still waiting for payment or even a response.

Even wondered if he had received the purchase order from ebay as there doesn't appear to be anywhere in my "messages sent" section of ebay showing that I even sent him one.  Yet I know I did as I have a copy in my personal email account with the verification number.  Is that standard practice not to have a history of purchase orders and invoices somewhere on ebay?

If there is I can't seem to locate it. 

The last item was purchased on the 19th.

Should I send him a friendly reminder or wait another day?

Both significant valued items.

Thanks.