Newsletter tab in admin backend disappeared after upgrade from 1.6 to 1.8.1

Question

I've recently upgraded a site from 1.6 and I've had some minor issues which I've mostly resolved now. My final hurdle is the newsletter tab which have mysteriously disappeared.

Any idea why it's gone and (even better) any ideas on how to get it back?

Even just suggestions on how to debug this issue would be appreciated.

Update:
I've experimented with creating a new user and giving this user a new role with only access to the Newsletter pages. Once I log in with this user I'm taken to one of the pages I have access to. I have toggled each newsletter page on and off and logged in and out for each to verify that all the pages work; and they do. The menu is still missing which confirms my theory that the update somehow broke the Newsletter menu entries. Any suggestions to how I can make the Newsletter tab (re-)appear?

Answer 1

You should check System > Configuration > ADVANCED > Advanced > Modules output > Mage Newsletter and verify that the output is enabled.

Answer 2

Go to app/etc and find Mage_Newsletter.xml file. If it is not there open Mage_All.xml and find

<Mage_Newsletter>
    <active>true</active>
    <codePool>core</codePool>
    <depends>
        <Mage_Core/>
        <Mage_Customer/>
        <Mage_Eav/>
        <Mage_Widget/>
    </depends>
</Mage_Newsletter>

If its not there add it. Also check if module Newsletter is present in app/code/core/Mage.

Update 1

Check if \app\code\core\Mage\Newsletter\etc\adminhtml.xml is present and if it has some content. All problems that you described could happen if it is missed.

Update 2

Go to System > Configuration > ADVANCED > Advanced > Modules output and check if it is enabled.