Because MailWise does not store your mail on a server, but rather works directly from your phone (so your information stays secure),
we cannot preview an attachment sent to you, but only download it completely and let you view it on your device itself.
This is why the "View" option (opening an attachment via the app itself) does not work, but rather you need to completely download the attachment to see it.
MailWise cannot show you a preview because we want only you to have access to your mails and information.
Once you go into the message, click on the icon and select "Download".
Then you can view the attachment on your device.