Can't Update to the macOS 15.4 RC? Here's Why

Some Mac users who have an M4 MacBook Air or M4 Max/M3 Ultra Mac Studio are unable to update to the latest macOS 15.4 beta that came out today, according to complaints on Reddit.

Multiple people have reported that attempting to download and install the macOS 15.4 release candidate results in an error message. "macOS could not be downloaded. Make sure you're connected to the internet and try again, or contact Apple support for assistance," reads the error.

It turns out that Apple failed to provide the appropriate decryption key for the M4 ‌MacBook Air‌ and ‌Mac Studio‌ models to install the update. Apple encrypts its software updates and a server-side decryption key is required for installation. The key for new Macs is not available from Apple's software server at this time.

If you have one of the new Macs that's running the software that it came with when it arrived, you won't be able to update to the macOS Sequoia 15.4 release candidate until Apple fixes the issue.

This problem will not affect new ‌MacBook Air‌ and ‌Mac Studio‌ models that were previously running macOS 15.4 beta 4, as these machines can install the release candidate.