An apparent software signing issue is interrupting updates for some Studio displays.

One thing that makes the Apple Studio Display unique, aside from the display’s native 5K resolution, is that it houses an iPad inside. The monitor includes an Apple A13 chip and 64GB of memory to support some of its smart features, and like any other Apple iDevice, it can receive iOS-based firmware updates to add new features and fix bugs.

But, as is the case with other Apple iDevices, this means that you will sometimes run into problems installing the latest updates for your Studio Display. This happened over the weekend to some users of Apple’s new studio displays who found themselves unable to update their factory firmware (version 15.3) to the latest version (15.4).

The reason the update stopped working is likely due to the way Apple handles iOS software updates. Apple verifies the digital signature of an iOS update file before allowing installation to prevent installation of updates that contain malware or other modifications. And to prevent downgrading to older versions of iOS, Apple typically only allows one or two of the most recent iOS updates to be installed at any given time. When a new version of iOS is released, as it did with iOS 15.4.1 on March 31st, Apple will stop signing the previous version (in this case, iOS 15.4) shortly thereafter.

The problem for Studio Display was that it did not receive the 15.4.1 firmware update along with other iDevices. This in itself isn’t a problem as the Studio Display doesn’t connect directly to the internet and isn’t subject to the same security vulnerabilities as a typical iPhone or iPad. But this was a problem for people who received new studio displays that shipped from the factory with version 15.3 firmware installed. Connected Macs could see that the displays weren’t running the latest firmware, but Apple no longer signed iOS 15.4, so the displays couldn’t actually install the update after downloading it.

As of April 10, Apple appears to be signing the 15.4 update for Studio Display again, allowing firmware updates to be installed normally. These updates are signed on a per-device basis so that older iPhones and iPads can continue to install the latest software they support, meaning that Apple will generally be able to release new iOS updates without having to update Studio Display and vice versa. -vice versa. In the case of the 15.4 update, as Macworld suggests, it’s possible that Apple simply forgot that it needed to keep signing the Studio Display update.

Firmware 15.4 was the version our review unit was running when we tested it, so it doesn’t include the promised fixes for the mediocre picture quality of the Studio Display webcam. According to Apple’s release notes, version 15.4’s main feature (apart from “minor stability improvements”) is support for Boot Camp on Intel Macs.