Both "Turn Passcode off " and " Simple Passcode" is greyed out

If the Turn Passcode Off button is greyed out, passcode restrictions are likely enforced on the iPhone (via a corporate configuration profile, mobile device management or Exchange policy).

Where passcode restrictions are set on a managed iPhone, they also affect Apple Watch. In such cases, it will not therefore be possible to turn off the watch's passcode.

If your iPhone is managed in this way, contact your device administrator for further information and help.

More information:

If you forgot the passcode for your Apple Watch - Apple Support

Turn off screen time.

And????

Check on time limitation if you disabled the option to change passcode