Try drag and dropping the image in a web browser.
After the browser opens the image, right click and save the image.
Then try opening it in Photoshop.
You said that you can open it in paint.NET, you can open the image in paint.NET and do save as...and save it as a new file.
Then try opening that new file in Photoshop.
Those two methods as a rule give a result; otherwise, you may use adobe psd repair tool by other ways like