The fact that opening a document as an attachment points to a couple of possibilities, but none of them matches your screen shot...

For example, there is a setting in Word 2013 causing uneditable files (such as e-mail attachments) to open in Read Mode, but then you should see the ribbon (menus) for Read Mode, but what you are seeing is the usual Home tab, but no other tabs.

Also, the document could be opening in Protected view, but then you should see the yellow bar with an option to activate editing.

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Stefan Blom
Microsoft Word MVP

Microsoft 365 apps for business
Windows 11 Professional