Can't edit page in Sandbox mode

Summary:

Can't edit page in Sandbox mode

Content (please ensure you mask any confidential information):

Hi, we are trying to change a simple field label on the Manage Items page in Product Information Management (PIM). I created a new Sandbox with all Tools selected and made sure it is in Edit mode as shown below.

When I go to the Edit Item page and select 'Edit Page' under the Administration menu nothing happens. I would expect the grey bar to appear at the top that indicates you are editing the structure.

All we are looking to do is change the name of the label for the 'Long Description' field displayed above. Thank you in advance!