An error occurred during updating
These are some of the solutions to fix the i OS 12 – i OS 12.4 Software Update Failed error on your device and download and install it successfully. When updating i OS 12.4, but with message noticing: “Unable to Install Upgrade. These solutions also applying to fix the same issue when installing i OS 11.
I also tried to verify integrity of tool files, and it said files checked out OK, but I'm still getting this error when I try to run.
The huge amount of traffic on Apple servers means that it will sometimes fail to keep up with some of the requests.
Therefore, it is best to wait for a few hours or days before trying again, as the load on their servers will be reduced.
As a last resort, you can manually download the i OS 12.4 IPSW firmware file for your i OS device, and use it to update your device.
This usually fixes the issue as you no longer depend on Apple’s servers to download the firmware file.