"File doesn't work, it's all white." This is a common question I receive from clients. Not all, but some of my newer files have a white layer over the top of the mockup layers. It can appear like the mockup is blank if you're newer to the mockup world.
So why the white layer Jen? : it reduces the file size drastically. By adding the white layer, your computer doesn't have to show a thumbnail which saves space. This is also very valuable to my biz because some sites cap their upload file size and between the white layer and compressing... I can get very large files below 20MGs!
So what do I do with the white layer Jen? : Go to your layers panel and either delete or hide (eye icon) the white rectangle on the top and voila, your mockup is ready for you to work with.
If you have a ton of larger PSD files, adding the layer is a good option going forward to save space on your computer and/or e-commerce sites.
Just a little trick I learned along the way!.