Hi @Phil Jones ,
Sorry for the inconvenience that happened to you.
According to my research, if you attempt to share an attachment from Word, Excel as an attachment /PDF, the new Outlook will not work as expect. This is the known issue and will be fixed in future.
Currently, the feature is in the "Rolling out" status for the New Outlook. This may not yet be available to all applicable customers.
For your reference:
Outlook: Sharing Word, Excel, and PowerPoint local files through the new Outlook for Windows
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