Photoshop CC: Why blend, sharpen, dodge, burn tools do NOT work in select color channels (both LAB and RGB)

I tried to use the blend tool in the A channel in the Lab mode and it didn't work. Then I saw the same tool didn't work in the separate red, green and blue color channels in the RGB mode. Is this a problem with my photoshop CC (latest version) . Thanl you very much for your help.

Blend, Sharpen, Dodge, Burn didn't work either in select color channels in both RGB and LAB.