KB - Outlook attachments are disabled

There are a few reasons that the Outlook attachment integration feature of PKZIP / SecureZIP could be disabled.

The option could be toggled off. To toggle back on left click on the Attachments icon in the system tray to toggle the feature back on.
Outlook could have the plugin disabled.

Outlook 2007	Outlook 2013
Click on Tools \| Trust Center Click Add-ins on the left column Locate the Manage dropdown towards the bottom \| select Disabled items Click Go If you see the plug-in listed, then enable it. Restart Outlook.	Click on File \| Options Click Add-Ins Locate the Manage dropdown and select Disabled Items Click Go If you see the plug-in listed, then enable it. Restart Outlook.

Disabling Outlook Integration

If you do not wish to use the integration feature you can disable it by going into Options | Mail | and uncheck "Zip Attachments"

Outlook continues to disable PKZIP Attachments

Customers installing PKZIP Attachments onto Windows Desktops running Outlook 2013 through 2016 may find that integration with Outlook is silently disabled by Windows.

After installation of PKZIP and SecureZIP for Windows Desktop onto a Windows Desktop running Outlook 2013, customers may no longer see PKZIP Attachments within their Outlook mail editor and PKZIP Attachments may not appear in the Outlook Add-Ins list. A change in Outlook 2013 by Microsoft can silently disable third-party Add-Ins on program startup causing the add-ins to stop operating. The information that follows discusses how to re-enable the operation of PKZIP Attachments with Outlook.

Resolution:

Customers may resolve this issue by completing the steps that follow. To complete this, they should be familiar and comfortable with viewing and editing Windows registry settings.

Close Outlook.
Open the Windows Registry and view the following entry.
\\HKEY_CURRENT_USER\Software\Microsoft\Office\Outlook\AddIns
If there is an entry here called PKZC.PKOutlookAddn, this entry should be deleted.

There is a similar entry under HKLM, this should not be changed, only the entry under HKCU is to be deleted.
Close the Windows Registry and restart Outlook.
On start, the customer should see a dialog from Outlook that appears as shown below and that asks to disable.
Add-Ins:
Choose “Always enable this add-in” for “PKZIP Attachments”.