The number of Bitrix24 administrators depends on your plan. Therefore, when changing a plan, you maybe need to change the number of active administrators.
Go to the Employees section and search for administrators in the filter.
If there is no Administrator field in the filter, you can add it. Click Add field.
The list of active administrators will appear. Click on the name and go to the employee's profile.
Choose Revoke admin permissions in the Administrator menu.