Problem: I am unable to add an attachment when creating a new Ticket Note.
Resolution: Below are some recommendations and settings you should have in place in order for this to work:
It is always recommended to use workflows to send these Emails to the clients.
If you are using a manual notification method, the checkbox should be selected before you hit "Save (S)" in order for the attachment to be successfully sent.
Multiple files can be selected and all of the attachments will be sent across.