Whenever I try to access eBay.co.uk homepage, or any page on .co.uk in general, I constantly get a HTTP 431 error.

I tried clearing cookies and cache, but it does not fix the issue. The issue remains.

I tried logging in incognito mode - that seems to fix it.

Yesterday I logged in on a new browser - that fixed the issue, but this morning that same new browser gets the error as well. 

I can't seem to find out the root of the cause. 
Have eBay updated and broken something?

Anyone else facing this issue?