App fails to work on Mac Os catalina.
That’s an 11 year-old build, which is really stretching.
According to the supported devices article, you need a minimum of 1 GB dedicated GPU memory, while your machine only has 512 MB.
That’s likely to be the problem.
It’s possible that upgrading the OS using OpenCore Legacy Patcher might help. This is just a guess, something to try. It would provide updated Nvidia drivers. Catalina has been unsupported for years so it’s not safe to use on a machine connected to the Internet.
The thing is, the OP’s machine’s current OS (macOS 10.15.7) is already within minimum requirements (macOS 10.14.4), so I’m not confident that upgrading the OS will help.
From the screenshots, we can see that Zwift is running. This iMac just can’t cope with the graphic requirements and so isn’t rendering properly.
Sadly, while the 27-inch, Late 2012 iMac was configurable when ordering it new to have a GPU with up to 2 GB of dedicated memory (the GTX 680MX), the GPU is soldered to the motherboard, meaning that this machine now couldn’t be physically upgraded to meet Zwift’s minimum requirements without replacing that extremely expensive component and/or paying for complex surgery.
Besides, it’s likely that Zwift will raise minimum requirements again in the near future, so any money would be better spent on acquiring a more recent device that is well within spec (which would cost less, anyway).
I’m not confident either. There is some chance that the updated Nvidia driver might help but I agree this machine is essentially too old and weak. However upgrading the OS would make it safe to use for other purposes, and would increase its value for resale or as a donation. Unless the mechanical hard drive has been upgraded, the performance will be very poor even if it works.
Thanks all… It was gathering dust and thought it might be up to the job… After several reboots attempts it works about 1 out 5 times. Time for an upgrade I guess.