Have recently stumbled across the wordpress cookie blocked issue.
Seeing as I write my own plugins I could hone in on the issue being something I’d developed. (by deleting my plugins (ensurinng I had a backup of course))
Or so I thought it was something in my code.
After extensive code removal I believe the issue stemed from a character set mismatch hidden in the bowels of whitespace as all my code is functioning again after being ripped out and put back in manually for testing bit by bit, and with the only major chnages being blank lines being removed and now magically the same code that wasn’t working before is working again.
Further, transporting the entire site and database to a windows apache/mysql env did not exhibit the blocked cookies.
Quite a frustrating issue.
Other information on the net talks about UTF formats so its likely my issue was this and buried in non visible character codes.