Could not find a part of the path

Hello, Community,
I used to upload images without any problems in my C# GH Visual Studio project( 24x24 PNG images for plugin icons), but I don’t know what happened; now, it gives me an error, even though I’m uploading from the same folder as before. Error emerges in both cases I save resources as byte format or as bitmap.
Can anyone, please, give a clue what the problem is? Thanks.