Pictures received in txts are showing up as files and can't be viewed nor downloaded

People are sending me pictures but they aren't displaying in the text thread. Instead they look like a file with a "?" and a download arrow. But tapping them does nothing - they can't be downloaded.

Pics from Android work. Pics from iPhones - some, not all - do not.

Someone posted this exact same issue a month ago but the only reply was 'reboot your phone'. Not helpful.