I've had issues with this when being sent pictures to upload to our website
I have asked people to switch their ipad settings:
1. Unlock your iPhone or iPad and launch ?Settings? app on your device and tap ?Camera? option.
2. Under Camera page, please tap ?Formats? option to set up photo formats when taking pictures and transferring to computer.
3. To disable HEIC image format, simply tap to switch on ?Most Compatible? from ?High Efficiency? option under CAMERA CAPTURE section
Any pictures I have been sent I've just used an online browser based tool