My icloud and find my iphone are greyed out

I had this problem (FindMy and iCloud greyed out in Settings) and, at least in my case, the generic Apple boilerplate answer given here is irrelevant.

What cured it for me, found purely by chance, was the discovery in Settings of "New Terms and Conditions" after a particular software update, which required you to open them and Agree.

This hidden, un-notified dysfunction had also blocked the phone's access to iCloud so no backups had happened for weeks. Both now work.

Well done Apple, thanks for your nobbling my phone without telling me (and evidently many others).

If an app or feature on your device is not working, not appearing, or is restricted (grayed out), it may have been disabled using Screen Time, or by an IT administrator if you are using a device owned by an employer or educational institution.

- Read this support article If your Apple ID or other options are greyed out in Settings —> If your Apple ID is greyed out in Settings - Apple Support

Tap Settings > Screen Time > Content & Privacy > scroll to Allow Changes and turn on.

- If the device is managed (Settings > General > VPN & Device Management), contact the IT department that is doing the managing.

When you go into settings, you will see “Agree or Review New Terms and Conditions” in blue that you can click on. Once you click that, the next screen will ask you if you agree to the new terms. Once I agreed, the Find My iPhone and all the devices returned to normal. Hope this helps!