If you are not able to login to WMserver using any users including root user, follow the below steps to enabled your disabled users.
Please create a new super user to login the WM,
Open command prompt, enter cd C:\Cambium\WM\server\bin (Your WM Installed directory)
Enter createSuperUser.bat db_user_name db_password new_superuser
For example, createSuperUser.bat wms wms test
Then, login using new user (test).
Go to Tools>Administration>Security Administration>Users
Select disabled user, on right hand side a panel will open. Go to User Profile Tab and click on "Setting Profile"
Uncheck the option "No Change in Status" and change the value of "Select the status to be set for this user" to enabled.
In this way you can enabled your disabled users. Please see the attached screen shots for reference.