Summary

Accounts that were previously provisioned and deactivated through the IdP, are not able to be reactivated in bulk through the Managed Accounts page.

When directly accessing the user's profile, and clicking the Reactivate Account button, the account is reactivated. So it's specifically related to the Reactivate button on Managed Accounts.

This does not happen for users that were deactivated but weren't provisioned.

How to Replicate

1. Provision a user through an IdP.
2. Deactivate the user through the IdP.
3. Delete the user from the SCIM directory or delete the SCIM configuration.
4. Go to admin.atlassian.com > Directory > Managed Accounts. 
5. Mark the deactivated user and hit the reactivate button. 
6. A pop-up is shown the user is reactivated, but you'll see the user remains in a deactivated state. 

Expected Results

Users should get "Reactivated"

Actual Results

Users remain in "Deactivated" status.

Looking at the developer tools it seems the endpoint activate (https://admin.atlassian.com/gateway/api/users/XXXXXX/activate) is not being called. This could be due to the members endpoint (https://admin.atlassian.com/gateway/api/adminhub/organization/XXXXX/members) returning the attribute "active" as "Blocked":

 "active": "BLOCKED",

Workaround

In Managed Accounts, view the User's profile, and click the Reactivate Account button to reactivate the account.