Why does error 2015 show when I restore my iPad?

Why does error 2015 show when I restore my iPad? The status bar shows that it is extracting the software, after extracting, a dialogue box saying "Allow accessory to connect?" shows briefly, and then error 2015 pops up? How do I fix it?

I've tried the basic troubleshooting steps, which are:

1. Checking that my Mac is updated
2. Deleting the iPadOS file from `~/Library/iTunes/iPad Software Updates` so that Finder re-downloads it
3. Checking if my iPad is in good condition; there are no hardware nor software issues
4. Checking if my USB-C to USB-C cable is in good condition and if it's the original one provided in the box
5. Trying to download the .ipsw file from Apple's CDN and then holding the Option key to manually select the downloaded restore file (it still shows error 2015)