Symptoms

Offline Activation file does not contain all intended keys.
This can cause a lower number of seats than intended.

Solution

All active, non-expired keys that will be used in the Protect console must be entered in the primary box under Help > Enter/Refresh License when generating the offline license file.

Solution

Once the active, non-expired keys that will be used in the Protect console have all been added in the primary box under Help > Enter/Refresh License, click Create Request.
You can verify all necessary keys are included in the LicenseInfo.xml file by opening the file with a text editor and verifying that all keys are listed.

Alternative Solution

If an offline activation file (LicenseInfo.xml) was created from the console already and only needs to have a key added or removed, this can be done by modifying the file in a text editor.

Adding a License Key to LicenseInfo.xml

Locate the current list of license keys:
<a:string>1234123412341234513135121</a:string>
and copy /paste the tags immediately after the current key. Next add the additional key to this new set of tags.
<a:string>1234123412341234513135121</a:string> <a:string>67896789678967896789</a:string>

Removing a License Key from LicenseInfo.xml

Locate the current list of license keys, and delete the key and its surrounding tags.
(Original)
<a:string>1234123412341234513135121</a:string><a:string>ABCABCABCABCABCABCABCABCA</a:string>
(Deleted Second Key and corresponding tags)
<a:string>1234123412341234513135121</a:string>