Well a Sony firmware update doesn’t work on a cluttered Mac, that has lots of apps on it or is attached to many devices. I had the same problem. In particular anti-virus and some other software doesn’t allow a Mac to discover the attached Sony camera.
Solution for my late 2013 “trash can ” Mac Pro:
* Duplicate the cluttered internal drive, an SSD in my case, to an external bootable device so that your Mac can run from that. Make a backup.
* Then reformat your internal drive and install a virgin macOS on it, in my case Mojave, as I needed to update my A7R Mark II and the Sony firmware update wouldn’t run on a newer macOS.
* Then only download the 2 pieces of Sony apps required for the firmware update.
* Detach all devices, remove memory cards from camera, have a full battery, and follow update instructions, run on the fresh internal macOS.
That has worked like a charm for updating the A7R.2, A1 and numerous Sony lenses.
Although I have not tried it, the A1 firmware update should also work on a fresh install of Catalina, Big Sur, and Monterey. According to user experiences the latest firmware update also seems to work on Apple Silicon computers running Big Sur or Monterey.
Good luck!