You could be stuck in a loop persisting from eBay blocking you. Try the usual, switch off the compatibility view, clear out cookies and cache and reboot. If this does not work make sure you have the latest version of your browser. eBay will not be running on older versions as a security measure.

 

change to another browser if problems cannot be fixed, as eBay is more compatible with Firefox and Chrome than with IE.

 

the other thing is, if using a mobile device, best to use the browser in full or classic view, not the mobile view. The eBay app is also fraught with problems so best to use a browser.

Thank you amber-eyed-girl for that.
I have found no trouble with any other messages after that one I had trouble with, a second question from a buyer (he had pressed 'buy', but after I had sent him the invoice and pick up details he sent a second question...would I take less? And his phone number)
He had included his phone number in the 2nd question, obviously thinking that I would phone him, which I never do, as I like to have a message trail through eBay messages, just in case.
I was trying to tell him after the 'offer' question that he was now the buyer, and had 4 days to pay.
That was the message that eBay blocked, saying that neither the buyer or seller were able to send their email addresses through eBay messages.
Actually, after someone presses 'buy' their email address is right there for me to see anyway.
I asked eBay to answer it for me, to tell him he was a buyer now, not an offerer.

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@wilk1149 wrote:
As a user of the eBay app for years now I have never had a problem sending or receiving messages

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I have, on an iPad.

I was given mine, but thanks for your comment 🙂