Animating Material Properties

Hi I have been trying to figure out how to change a materials properties while using U-Motion so that they can sync up with my animations, I thought I figured it out but it doesn't seem to be working.

In order to test this out first I made an incredibly simple material shader in amplify shader editor, just a float property in the albedo that changes it from black to white with a min and max slider.
It can be adjusted in the inspector tab with the material and I've also tested it with the regular animation window and it seems to work fine there.

So with U-Motion after a bit of sleuthing I realized I can add custom constraints that adjust component properties in the same way u-motion affects its blend shapes. So I added a custom constraint changed it to component properties, selected the mesh, used the ... to select skinnedmeshrenderer, material, property. Checked preview added constrain input so it can be a slider.
Went to pose mode and it doesn't seem to work.

Unlike blend shapes moving the slider doesn't appear to do anything to the material property. I tested in the unity animation window and it works there. It was also listed with the mesh in a category under skinnedmeshrenderer along with the blend
shapes.
I tried key framing the different value points in u-motion but it doesn't seem to change anything either.  Again I did the same test in the regular animation window and it worked fine there.

I will admit I am still super new to Unity, U-Motion and shaders so I could have missed something obvious but I have spent too much time today trying to figure this out.

My ultimate goal with the shader was to use a 2d Texture to animate the mouth and possibly some other special effects through properties during animation so not being able to preview them while animating the body will be rather annoying too say the least.

I can take and post some example photos later if it might help, but its late and I am tired.

Thank you in advance for your help

-Z