iPhone Activation Error: Stuck on “Update to Activate”

An iPhone 7 is stuck on the “Update to Activate” screen after a restore and update via iTunes. All update attempts fail with the error “Activation Server Unavailable.” Restarting the computer doesn’t resolve the issue. The only solution found was to perform a hard reset while the phone was updating in iTunes to break the update loop. However, after escaping the loop, the original “Activation Server Unavailable” error persists. Apple Support suggested trying a different SIM card from the carrier. A solution for the “Activation Server Unavailable” error has yet to be found. While a hard reset during the iTunes update process can break free from the “Update to Activate” screen, it doesn’t address the root cause of the activation error.