Yes. My latest try... I first searched my entire hard drive for any leftover itch files. Found an itch.app where I didn't expect it and used AppCleaner to remove it and its files. Then I DL'd a fresh installation app. It didn't get stuck at setup, but I still got that same error when trying to log in.
My computer is an iMac 12,1 running 10.11.6 (El Capitan).
Processor: Intel Core i5 2.5 GHz.
Memory: 16 GB 1333 MHZ DDR3.
I don't run any virus software or anything like that. Macs are pretty safe as long as you don't download indiscriminately. I tried your suggesting about DL'ing the archive file, but I didn't get a .zip file, just a file my Mac didn't know what to do with. Its name: "Unconfirmed 382498.crdownload".
Isn't there a repository of previous itch.app versions where I can DL an earlier one? Because it seems as if it's this new update that's the issue, at least for me. The app was working perfectly before this. Lastly, I really appreciate all the work you're putting into this...thank you!