Users require a special Position, called Administrator, in the project's User configuration to access the web Management Console.
The Position is created by default with every Bizagi project; you just need to allocate it to all users who should have access to the Management Console.
To do so, login to the project's Work Portal as an administrator and access the Admin - Users menu.
Navigate to the user who you will grant the Administrator permission to, and go to the Organizations tab. In there, include the Administrator permission and save the change.
For more information about Users configuration please refer to Users Administration.