First I have faced the following error "session_start(): Failed to initialize storage module: user (path: /home/sitename/html/app/storage/sessions)"

for this issue I have add the following line in /home/sitename/html/vendor/symfony/http-foundation/Symfony/Component/HttpFoundation/Session/Storage/NativeSessionStorage.php

ini_set('session.save_handler', 'files');

After that "The SessionBagInterface attributes is not registered" issue occurring.

Kindly help me to fix the issue I have upload files in live.

well i think i have met such conflict before .. i guess you should clean the cache of your browser then try again hopefully that would help