I have just upgraded TYPO3 from 10.4 up to 11.5
When I attempt to login to the backend, the login form submit takes me to a 404 page.
mysite.com/typo3/login?loginProvider=1433416747
The frontend appears to be working, and the install tool is working.
If I run vendor/bin/typo3cms it tells me:
TYPO3 Console 7.1.6
TYPO3 CMS 11.5.33 (Application Context: Production)
TYPO3 is not fully set up.
Command list is reduced to only show low level commands.
Not listed commands will not work until TYPO3 is set up.
Run "vendor/bin/typo3cms --all" to list all commands.
Some commands could not be configured and are missing in this list:
Command name: "scheduler:run", error: "The requested database connection named "Default" has not been configured."
Command name: "impexp:export", error: "Warning: Undefined global variable $LANG"
Command name: "impexp:import", error: "Warning: Undefined global variable $LANG"
How do I fix this?
An important ("breaking") change between TYPO3 v10 and v11 was the introduction of human-readable URLs in the TYPO3 backend (also known as "deep-linking", see the release announcement for further details).
A typical root cause of a 404 error when logging-in after an upgrade is an invalid/outdated webserver configuration (rewrite rule). TYPO3 tries to migrate the configuration automatically but this can fail if you don't use the default configuration shipped with the TYPO3 Core, or if you don't use Apache httpd.
If you're using Apache, check if the .htaccess file exists. Follow the migration instructions documented in TYPO3's change log.
Once you can login at the backend again, make sure that all post-upgrade tasks have been completed.