why PS can’t show studio recolorables mesh normaly？

Hi wdmzjyy, welcome to Studio forums. Are you exporting the image as a .dds or as a .png? If you are exporting as .dds does your Photoshop have the necessary .dds plug-in that allows it to work with .dds images? Try exporting the image from the .package as a .png instead of as a .dds and see if that solves the problem. The .png format is easier to use (in my opinion) and Photoshop does not need a special plug-in to work with .png.

If you are using Photoshop you will not need the Paint.net plugin that is mentioned in the What you will need section and you can use Photoshop's features to add the shadowing to your recolor image instead. Since I don't use Photoshop I can't really be more specific about how to use it to make a recolor but at the end of your recolor process you want to have an image that looks similar to the one in the tutorial. This image will have your painting and frame texture positioned as they are shown in the tutorial and you want the rest of the image to be entirely filled with a solid color that matches the edge color of your texture.