I selected some (not all) of the photos on my iPhone to import into a Lightroom folder. Worked fine. When I attempt to import again (to add photos to a different folder), it shows there are no photos to import. This happens every time. I've tried it with 2 different iPhones. If I then close/reopen Lightroom, the photos are there to import.
Can you give us software version numbers?
Lightroom Classic CC (Help > System Info)
I'm fairly sure this is a bug in Lightroom import and report