Admins on your domain may not be able to access Vault, even though you have purchased and distributed Vault licenses to one or more users. When the admin tries to access, he or she will get an "invalid request" error or a message stating the service "has not been enabled." 

How to diagnose:
You can confirm that you are affected by this issue by taking the following steps:

a) Confirm that Vault exists and is turned on for the affected user(s).
 1. From your Admin console dashboard, click on Google Apps.
 2. Verify that Vault is included in the list of services displayed, and that it is enabled (for all users, or at least for the user in question's organization).
 3. If the Vault service is not listed or not turned on, please contact us.  

b) Confirm that at least one user has a Vault license.
 1. From your Admin console dashboard, click on Billing.
 2. Click on the key icon to the far right of Google Apps Vault to manage your vault licenses.
 3. Click on Assigned users and confirm that there is at least one user with a Vault license.
 4. If none of the users have licenses, please contact us. 

c) Confirm that the admin does not have the Vault service included in their Google Apps list.
 1. Access the user's details by searching for them, or by clicking on their name in the Users list in the Admin console.
 2. Click on the Google Apps Enabled section of the user details, and verify that Vault is not listed.
 3. If Vault is listed, please contact us.

If Vault is enabled, you have assigned at least one Vault license, and your admin(s) still don't have the Vault service in the Google Apps Enabled page, then you are likely affected by this issue, and should review the workaround instructions below.

There is a workaround for this issue, but it requires provisioning one additional Vault license temporarily to enable the admin(s) to access the service.

1) From your Admin console dashboard, click on Billing, and then click on the key icon to the far right of Google Apps Vault.
2) Click on the Unassigned users tab, and find the name of the admin or admins who requires Vault access.
3) Check the box next to each user who requires access, and then click Assign > Google Apps Vault. Confirm that you want to assign new licenses.
4) Wait 10 minutes, and then click on the Assigned users tab on the Google Apps Vault billing page.
5) Check the box next to each admin you just added, and then click Unassign. This will remove the newly added license.

Adding and then removing the license for these admins should resolve their Vault access issues.

Please make sure you DO NOT remove licenses from anyone who's email you wish to retain using Vault. A user must have a Vault license in order for Vault policies to be applied to that user.