well I do not know Patran but it often happens that older files cannot be opened by newer versions of the program
Sometimes there are 'import' options for older files...
You might want to read the program manual and/or read on their homepage
I am not familiar with the Patran. However, depending on the error message when the file is loaded, if the file is very old and in binary format, I suspect that such file is obsolete and cannot be read anymore. You could verify this with Patran's support team.