This Computer Back up now greyed out

Try this:

Set Auto-Lock iPhone to Never.

Disconnect the iPhone from the computer and connect again with the original Apple cable.

Do you still use Windows 6?

Windows 6 is Windows OS Vista (Januari 2007) is an outdated OS, is an unsupported version of Windows

Microsoft say goodbye to Vista in 2017.

I hope you use Windows 10 now.

Just test here with Wiindows 10 - version 21H1,  iTunes version 12.12.2.2 and it works.

Not sure the iOS version of your iPhone.

It's still strange, try again next week.

You may need to log out and back in to iTunes on your Windows laptop.

See also this Apple article: If you can't back up your iOS or iPadOS device to a computer or restore it from a backup

https://support.apple.com/en-gb/HT203271

If you need more help ->  contact Apple Support.

Thanks for your feedback and you're welcome.

Still will NOT let me click Back up Now

Restart the computer and try again.

Do you happen to use an antivirus program?

Maybe turn it off, as I don't use an antivirus program (not sure if this has anything to do with it).

A question: Did you click in the circle at iCloud or This Computer?