Radio displays "No CLK"

[Curtis629]

Searched and couldn't find so I'll ask. I just bought a 98 xlt with the cd/tape factory stereo. It doesn't display the time like my 2000 xlt does with the same radio. When I press the CLK button it flashes "No CLK". Is it a a bad head unit or is something else not plugged up, fuse blown, am I doing something wrong?
Thanks for all the help.

Everything else seems to work fine on the head unit.

 

[jad2411]

My 06 radio doesn't show the clock either, I read that there's a way to configure the settings, but I think only a dealer can do it