Title says it all. I can adjust the channel hue and saturation on any image but the shadow tint slider has zero effect even dragged to the maximum unless I am using a raw file. Sometimes I have older TIFFs or JPEGs and want to use that slider, but I can't.
Try resetting your LrC preferences file as detailed in the below article. It can resolve many unexplained issues. Place a copy of the current Preferences file on your desktop so it can be easily restored if the issue persists. See if that fixes the Shadow control issue. I assume by Shadow you mean the Luminace control. Is that correct? If not show us a screeshot of the control.
I agree with @thedigitaldog The Calibration panel Shadows control only works with raw files. For JPEG and TIF files you could use a Luminace Range Mask with its Tint control. What specifically are you trying to accomplish?