For some reason I don't get to post on page with all the so-called solutions involving Akamai security or VPN's, but I seem to have found the actual solution, at least if you're using a Chrome browser.
Had never seen the problem since joining up 20 years ago, it first appeared a couple of weeks ago when I was denied access to reply to message, so buyers were sending me messages and I couldn't reply. Didn't know what to do, waited a couple of days - during which everything else on the site worked normally - and it went away. Then today couldn't access anything, didn't even have permission to go to ebay.com. Used my neighbor's computer next door and it worked fine so knew the site wasn't down (which wouldn't have surprised me given all the problems at the moment).
So tried clearing my cache, no difference. Then cleared my cookies and browser history - and everything worked fine again. Given that I hadn't rebooted - that was going to be next - my IP address hadn't changed, that wasn't it. I'm not using a VPN either. I'm not a tech type, but seems pretty clear that ebay itself is the cause of the problem and not whatever methods and routings we're using to access the site. Poisoned cookies????
