After upgrading you may find that your Marketing menu is missing all the Newsletter\Email Campaign menu items. Sitefinity has a knowledge base article on how to fix it but it doesn't work so well if you are storing your configuration in the database.
You can read the the knowledge base article on the Sitefinity site. I had something similar except that the module didn't list any errors but all the menu items and pages to manage them were missing. I am not sure at what point this happened because the feature was not being used. It wasn't until I decided to use it that I noticed it was missing.
For this setup the configuration was stored in the database. So when following along the article details I needed to go into the database table to change the config information. But after trying this, it didn't work. I also tried uninstalling the module but it would never show as being uninstalled. Always deactivated.
The issue ended up being that I also needed to change the file based SystemConfig.config in the configuration folder of the site. It appears that after reading the database version it then went and read the file based version which still had the module as activated. So the result was that the Module stayed deactivated????
The process of checking the database and failing back to the file system is by design. At the point you move the configuration to the database all the current file configs are kept as the defaults.
To fix this problem here is what I did in my test and then prod environments.
In the database table, sf_xml_config_items, find the system config xml and mark the Newsletter as <add startupType="Disabled" name="Newsletters" /> . Make sure you do not have the version attribute present. Then do the same in the file version. Restart the site. Go to the back end Administration -> Modules and Services and you can then select to Install the module. The module installs and you will have the items back.
It appears that if you leave the version attribute on the element then this indicates to the system that the module is deactivated. When it is removed that means it is uninstalled.
This got me going. Hopefully if you are having trouble getting this module back this may help you out.
Thanks for reading and feel free to comment