Just upgraded from 220.127.116.11 to 18.104.22.168 and all is well - except - the site has two stores and now logging in as a customer in the second one causes a loop. which eventually just kills it with a This webpage has a redirect loop message.
It works on the old server (22.214.171.124) and I have tried it with both the original .htaccess/index.php and new (copied from the root with the site code put in the bottom) .htacess/index.php in the proper subdirectory. Aside from replacing these two files with copies from the new version of Magento all the settings remain intact.
Anyone have any insight?