my itunes back up now button is greyed out so suddenly I can't back up my iphones to I tunes

Hello dave-wilson,

If you can't back up your iPhone to a computer you learn how to resolve the issue by following the steps here: If you can't back up your iOS or iPadOS device to a computer or restore it from a backup - Apple Support

These steps may help:

Try again after each step

1. Make sure your Mac or PC is up-to-date. If you're using iTunes, make sure that you have the latest version of iTunes.

2. Connect your device to your computer with a USB cable, and locate your device on your computer. If your device doesn't appear in Finder or iTunes, learn what to do. If you forgot your passcode or your device is disabled, learn what to do. 

3. Restart all your devices.

4. If you use a Mac, skip this step. If you use a Windows PC and iTunes won't respond or your backup never finishes, you might need to update, change, disable, or uninstall your security software.

5. If you own more than one computer, try to make a backup on your other Mac or PC. Or, use iCloud to back up your device and restore from your iCloud backup.

6. If you see an alert that says an error occurred, your backup is corrupt or incompatible, or there's not enough disk space, find your error message below to learn what to do next.

7. Contact Apple Support.

Thanks.