Mmmm, out of curiosity, are the phone app users getting an error saying something along the line of- error, does not support app, log into ebay.com.au???
*we may be human, but we are still animals*

I just answered a similiar question on the same problems I have been having:- 

 

"I have had several issues with Buyers telling me that they cannot pay. 

 

I have resent invoices and still nothing for them to pay.

 

After lots of investigation I have realised that after changing some of my postage policies, much of the information has "dropped" off.

 

My issue seems to have been the "postage option" 

 

I changed the invoice to "standard delivery" and all went through fine on the last problem item"