I made the mistake of upgrading a perfectly running 2.1.8 beta / BI installation to CPAI 2.1.9 beta. Now only get 404 errors. Uninstalled, deleted the Codeproject folders, rebooted, re-installed 2.1.8, and still only get 404 errors.
Make sure when install CPAI 2.19 ro 2.18 to give it at least 20 minutes or so to fully install modules. I f BI tries to start module before it is installed it seems to hose the install. Just uninstall the module and then reinstall and wait for it to complete before starting BI. Anymore, I just uncheck the use AI in BI settings/AI
And then sometimes you can upgrade without doing anything