How do I transfer photos from a Pixel 3 to my iMac?

Can someone please tell me how to transfer the photos from my Google Pixel 3 to my iMac?

I have tried connecting my Pixel 3 to my iMac, and then opening Photos on my iMac but I get an error message saying "Cannot import 17 items - some items cannot be added to your Photo library because they may be an unrecognisable file format or the file may not contain valid data."

I have downloaded the 'Android File Transfer' app and each time I open that app, it says "Could not connect to device - try reconnecting or restarting your device." I have re-started the phone and it still gives the same message.

I have also tried connecting a memory stick my Google Pixel 3 and I still cannot seem to get the photos to transfer.