"No add-ins currently available." when deploying add-in using Centralized Deployment

I am trying to deploy an add-in with add-in commands on the desktop version of office 365, using the Centralized Deployment method.

I followed the instructions for Centralized Deployment and the addin appears as "on" in the Office 365 admin center. I used both "Everyone" and "Specific User/Group", but when I open the Word application and go to Add-ins, under "Admin Managed" I see no addins , and the message "No add-ins currently available." The addin is'nt visible neither on Word 2016 Desktop (with subscription) nor Word Online. I have also tried deploying addins from office store using the same method (Centralized Deployment) but they also don't show up.

I have Word version 1708 (8431.2270), and I am using a developer subscription.

Do you have any suggestions to fix it or know why it is not working? Thank you.

Also, I noticed that I am getting a 403 Error when refreshing the Admin Managed tab (when calling https://euc-word-edit.officeapps.live.com/we/AddinServiceHandler.ashx)

Solution

I solved, by enabling Exchange, and my manifest had an issue. I changed <CustomTab id="HelloWorld" x:type="CustomTab"> to <CustomTab id="HelloWorld"> and it worked.