When I delete staff member in License and Security > Security Manager > member name > Delete I am getting error:
Delete Cannot delete 1 staff member(s). Reason: Deletion of last account member is forbidden.
User account is the only staff member on subscription on Operations > Subscriptions > subscription > Managed by tab.
Add new staff member:
Go to Operations > Subscriptions > subscription > Managed by.
Login to Customer Control Panel under administrative staff member.
In Customer Control Panel on Users tab add new user.
After that you will be able to delete first staff member.
Last staff member on subscription cannot be removed.