I can't write a sleep mode to an XBee via XCTU. Is the device damaged?

I can update the firmware. I can read/write other parameters. The Xbee is currently in SM 1. I can set it to SM 4. If I try to set it to SM 0, I get a write error. The Xbee device is a XB24-ZB, ZigBee End Device AT, version 28A7

That is because Digi’s implementation of an End device requires it to sleep. So trying to turn of sleep is not an option. Not without making it a Router.