Hmm...I've only just noticed but I did update iOS and macOS both within the last week. It's affecting me as I often send lots of pictures from my iPhone to my iMac via Airdrop and then I batch process the images on my Imac in Photoshop Elements.
Unfortunately, Photoshop Elements does not recognised HEIC image files. I'll reset the iPhones camera format to 'Most Compatible', which seems to be JPG format. There's also a huge difference in file size between HEIC and JPG images captured on my iPhone, which translates to a difference in image quality.