Why didn’t my iso 15.7.5 update didn’t update

Do you have it set to do that?

From: Update your iPhone or iPad - Apple Support

Customize Automatic [iOS] Updates

Turn on automatic updates

1. Go to Settings > General > Software Update.

2. Tap Automatic Updates, then turn on Download iOS Updates.

3. Turn on Install iOS Updates. Your device will automatically update to the latest version of iOS or iPadOS. Some updates might need to be installed manually.

I presume you tried to do this wirelessly? Make sure all the criteria in this article are met so it can do that: Update your iPhone or iPad - Apple Support

From ASC contributor Lawrence Finch at How can I upgrade my iPhone 6s iOS13 to i… - Apple Community here's a checklist of criteria that all need to be met in order to update wirelessly:

• You need at least 10 GB of free storage for iOS 16 or 6 GB for iOS 15 or lower; more is better

• You must be connected to a Wi-Fi network (and not a personal hotspot)

• 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 and must have a cellular data connection

• You cannot still have a beta version installed on the phone

• You cannot have a previous version that was downloaded, but not installed - go to Settings/General/iPhone Storage to look; if you find an iOS installer, delete it.