It sounds like you've reached the user limit for your plan.
If you do not have any available Writer and / or Reader users within your account (i.e. the add writer / reader user button isn’t showing) and you wish to add another user, you can either:
1. Delete an existing user. However, it is worth noting that:
- You cannot delete the Account Owner.
- A delete is permanent and cannot be undone. On deleting a user all of their clients, reports and private customisations will be lost.
2. The Account Owner can either:
- Increase the user limit by upgrading your plan, or
- Purchase another Writer or Reader User license.