Update

Do you have access to a computer? Windows PC with iTunes Or a Mac will work. If YES, then try and update your iPhone 6s Plus with the use of a computer. Review this guide published by Apple ➔ How to update your iPhone with a. Computer.

Axel F.

kaidence224 Said:

"Update: I have completely cleared all space required for the update, but it shows that there is not enough room still"

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To Clear Space, Refer to the following...

Troubleshooting iPhone Storage:

Internal storage cannot be upgraded. It is what it is. So, the maximum internal storage capacity never increases, even if you upgraded your iCloud plan. Learn More here: What's the Difference Between Device Storage and iCloud Storage? Apple Support

So, what to do:

Clear Space:

Try clearing internal storage though use of the following:

What Space to Clear:

A. Clear Temporary Internet Files:

Clear your Temporary Internet Files(Cookies & Cache) of Safari:

• Cookies perform remembrance of certain site-entered data.
• Cache keeps a snapshot of the last time you visited a site.
• Go Here: Clear the History and Cookies from Safari on your iPhone, iPad, or iPod Touch - Apple Support

Also...



B. Clean TV and Music Libraries:

Remove all unneeded files from your TV and Music Libraries. Full-Movies take up 2-4GB typically, and a bunch of those would take up a load of storage, ideally. So, if you have any movies that are not needed, then delete them.

Also..

C. Clear "Other":

Clear the storage named "Other". It basically contains unnecessary files such as caches that are used for system ease of use - all of which gather over time: How to Clear "Other" in your iPhone's Storage - Use Backup - User Tips. Caches would be being used for remembrance of application use. So, clearing other may be the way to go about this, as it would be performs through use of a computer.

kaidence224 Said:

"Update: I have completely cleared all space required for the update, but it shows that there is not enough room still"

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Use a Computer to Update:

Power off your iPhone, and perform installing this update using a computer.  Use this User Tip: Update your iPhone Using a Computer - User Tip

This video may help you.