Import of photos from iPhone to iMac hangs "Preparing to import from..."

My photo library is too big to fit on my 256 GB iPhoneX, my wife's much smaller library doesn't fit on her older iPhone SE. However, since a bout a year of well update MacOS I cannot move new photos from either iPhone to my iMac. I reinstalled the system on my iMac and got as far as the start of an import and then my whole system went down and now I am back to the hanging notification, false promise, that the iMac is Preparing to import ... It appears to be a problem on the iMac MacOS side of things since neither iPhone can transfer photos.

I do not know how to replicate a bluetooth transfer as one user suggests, my attempts have been by hard wire traditional USB A