okay i have one .psd file of an image i am editing, i want to insert another image so i open up the image in photoshop, ctrl+a, drag drop into my other file i want it in as a layer, and it shows the selected boundary of the image but the image is not appearing, even when all other layers are hidden. What is the problem with this?

Don't Ctrl+A
Use the move tool (ofc) and click-drag the image into the tab where your first file is and then drop it onto the image or w/e you're working on