For the Assessment Update option to become available, you would first need to ensure you have an Active Caretaking Arrangement record for the YOT case in question.
You may need an administrator to ensure you have the Caretaking Arrangements menu item. If you don't have this, an administrator can add this by following these steps:
Click Administration, then click your role.
Click Menu.
Add Youth Offending Caretaking Arrangements to the current menu items.
Following this, when you go into Connectivity Transfers, the Assessment Update option should be present alongside Full Data Transfer.
If you require further guidance, contact the support desk and reference this article.