Error 4013 despite repeated Restore Attempts - fix?

Just updated (or tried) to update my iPhone 11 Pro to iOS 15, but it got stuck in the refresh cycle. I have tried to do a restore but keep getting error code 4013. This error code continues to come up even after trying all of the different work around suggestions - updated iTunes, tried a different computer (PC & Mac) and have tried a different cable. Nothing is working.

What can I do?!