When sending an email you are no longer prompted to ZIP attachments.
Check PK Protect Settings
If you are not being prompted for all attachments, do you have ZIP Attachments enabled under PK Protect Options | Mail | General?
If you are only prompted for certain attachments, check the mail filter under PK Protect Options | Mail | General |Attachment Filter. Check to see if your file type is being excluded from the prompt.
Check Outlook Settings
Outlook may have disabled the ZIP Attachments add-in. Verify it is not on the disabled items list using the methods below:
|Outlook 2007||Outlook 2010|