the nastran input file does not exist in the specifiedf folder is my guess !
Have you actually check what you have in specifiedf folder ?
In the ribbon bar under "Home", hit the SOLVE button and select "Write solver input file". In the text window that appears, scroll up to find the directory the file was written to. It should say something like "Writing file <path_to_file>". Confirm that the <path_to_file> is the same as .\Solution_1 or whatever you want it to point it.