Q: error 23 not allowing download of new    updated ios

Howdy oldbaz50,

Welcome to Apple support Communities.

If I understand correctly, you're seeing an 'error 23' alert message in iTunes when attempting to update or restore your iPhone 6s. Try taking a look at the article linked below and running through the troubleshooting tips that it provides.

Get help with iOS update and restore errors - Apple Support

Check for hardware issues

If you see error 53, learn what to do. If you see one of the errors below, you might have a hardware issue:

• 1, 3, 10, 11, 12, 13, 14, 16
• 20, 21, 23, 26, 27, 28, 29, 34, 35, 36, 37, 40, 56
• 1002, 1004, 1011, 1012, 1014, 1667 1669

Here's what to check:

1. Make sure that you have the latest version of iTunes.
2. Check for issues with third-party security software.
3. Make sure that your USB cable, computer, and network are reliable. Then try twice more to restore your iPhone, iPad, or iPod.
4. If you still see the error message, you can check for outdated or modified software or contact Apple support.

Take care.