HEIC is an Apple image format that is not always compatible with other applications. For example, Speedgrader can not see HEIC files uploaded by students using iPhones.
You also can not import HEIC files into an Acrobat file. So, you may want to change the default image format setting on your Apple device.
Set your iphone or ipad to always use the JPG format:
- Open the Settings app on your iPhone.
- Tap Camera > Formats > Most Compatible.