Hi, I'm not conversant with the Sofortbild software as I use 'ControlMyNikon' with my D300.
I did have a quick look at the website for Sorortbild and noted the following comment;
"" Camera Support Sofortbild currently supports all newer Nikon digital single-lens reflex cameras including the high end models D4, D3s, D3x, D800, D800E, D700 and the consumer D300s, D7000, D90, D5100 and D5000.
Support for the older Nikon digital single-lens reflex cameras is optionally provided by a legacy feature.""
Is it a possibility that the D300 is in the 'older' category ?