iOS 15.4.1 does not work. It won’t upload.

To update over the air from the phone all of these requirements must be met:

• You must have an iPhone 6S or later (including any SE generation)
• You need at least 6 GB of free storage
• You must be connected to a Wi-Fi network (and not a personal hotspot) unless it is an iPhone 12 or 13 series with an active 5G network connection
• The phone must be charged to at least 50%, and preferably plugged in so it stays above 50% during the update
• The phone must not be in Low Power Mode
• The phone must not be connected through VPN, and it may be necessary to delete any VPN apps and VPN profiles
• The phone cannot be in Airplane mode
• You cannot still have a beta version installed on the phone

If you can't meet all of them you can still update using your computer.

6GB? It said 4.29GB before I downloaded it. It was enough of a struggle to delete enough stuff to get down to that figure. Is this why it says ‘Unable to Install Update - an error occurred installing iOS 15.4.1’? It downloaded fine, but won’t now install :-(

The download may be 4.29 GB, but it is an installer that must be run on the iPhone to update iOS. So it needs additional space to extract iOS from the installer.

If you don’t have the space you can update using your computer: Windows 7 or later, or any Mac.

kiki1015 wrote:

6GB?

Yep.

If you need more space for an update on your iPhone, iPad, or iPod touch - Apple Support

If you see Error 4000 updating your iPhon… - Apple Community

“Uploading” … how?

Are you using Wi-Fi (no Hotspot, no VPN, no anti-virus)? You should be.

Is your iPhone well charged? Does it have at least 6GB free space?

I tried on my laptop, but after several painful hours, it just came up with “The iPhone could not be updated. An unknown error occurred (4000).” Any ideas?!