If an account is marked for deletion, this article can provide you with the steps you need to reenable it.
How to get the account unmarked for Deletion
it can be resolved by an on-site administrator by following the steps below:
Open DeltaWMS with the admin account
Open Maintain Operators on the User Maintenance tab
Enter the User Code
Untick Marked for deletion
Click Apply
The account should now be accessible.
Need further help?
If this doesn't work, please raise this with Delta Support, and please include the user who has been marked for Deletion.