People always say that but it's rubbish unless the person has done something unusual when copying the file. Just drag the firmware file only to the card. It should not be compressed or in a folder. I have just updated my A7R5 to version 3.01 yesterday. I am using a Mac Studio. I'm pretty sure that if you want to use the Creators app to update the firmware you need to connect to your camera via WiFi.

Are you keeping charged batteries in the camera? It's possible the internal battery that remembers that kind of stuff is going bad. You could also try a full reset. 

Welcome here. You should check the SD card for hidden files MacOs likes to put there. Some camera models get irritated by them.