Can't import a 4.7mb png file into media pool

My apple Iphone 11 captures 4k photos and when I download such a still image from iCloud to my laptop it is a 4. 7mb png. However, when I load that png file into the Media Pool this is how it looks in the media pool:
Any ideas? (Incidentally, if I first open the file in Corel and re-save it (still as a png) then it becomes a much smaller (2.4mb) file that will import into Resolve (but, of course, with half the quality). That's a hint, I suppose, as to what the problem is but surely Resolve can handle a large png. There must be some other problem. JPG's import into Resolve just fine...just this problem with png's but it's killing me.
Thanks for any thoughts!
John
(no image, just the black box) and, though I can drag that blackened square (w/no image) into the timeline, I then can't do anything with it there.Any ideas? (Incidentally, if I first open the file in Corel and re-save it (still as a png) then it becomes a much smaller (2.4mb) file that will import into Resolve (but, of course, with half the quality). That's a hint, I suppose, as to what the problem is but surely Resolve can handle a large png. There must be some other problem. JPG's import into Resolve just fine...just this problem with png's but it's killing me.
Thanks for any thoughts!
John