.png Files/ Photo in the ATTACHMENTS is not opening up showing the following pop-up.
Paint Application is not supported in APM. To open up .png files the machine which you are working on APM should have PHOTOS or Paint 3D Applications.
The reason can also be if the Default Application set in the machine to open up .png files is set as Paint Application or Which APM doesn't Supports, If that's the Case you Can set the Default application as PHOTOS or Paint 3D.