can't logon after migrating site to new host

Hi all. Moving a site from one host to another. The domain URL is the same on both.
Tried using Updraft and Duplicator (to migrate the site), tried a manual rebuild of the site on the new server. But keep getting the following error msg: “ERROR: Cookies are blocked due to unexpected output” when using example.com/wp-login.php and the blank white screen when any other URL is used (ie; example.com/wp-admin/options-permalink.php).
Front end works fine unless the www. is used in the URL (gives blank screen on front end) but the admin logon just shows the error. I have disabled all plugins with no luck. Debug mode doesn’t show anything. Searched and searched – Running out of ideas. Really appreciate some help.
Site is here – example front end (bottom right button goes to blog)