why does the trackmat doesn’t work?

[Walter Soyka]

You are not using a track matte, you are using the “Preserve transparency” switch:
https://helpx.adobe.com/after-effects/using/alpha-channels-masks-mattes.html#preserve_underlying_transparency_during_compositing

Layer 6 will get its transparency from the composite of all layers beneath it, not just layer 7. Since you have only shown a sliver of your Ae UI, we can’t see if there are other layers there that may be affecting your composite.

If you want to use a track matte, put the Shape Layer ABOVE your footage layer, then choose “Alpha Matte Shape Layer 1” from the TrkMat column.

Walter Soyka
Designer & Mad Scientist at Keen Live [link]
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
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