Trying to open kn5 file - need help

I am trying to open a kn5 file using 3DSimED3 without success. The file doesn't open and the program closes automatically, coming back to the desktop;
Any idea would be more than welcome.
Thanks

I always open the kn5-files with 'file/import' (not with 'import as objects'. It generally works fine - only exception: corrupted kn5-files which occurs from time to time unfortunately...

Thank you for your reply.
I've found out that the files are locked by the authors, contacted them asking for unlocked files as I wish to convert files to GP4 for personal use only and they denied, even having paid for the MOD. It's the VRC Indycar MOD 2021.
In my particular opinion, the conversion of MODs made for another racing game to GP4 only aggrandizes and highlights the great work done by them. We are a small and faithful community, all work done by any of us has the main goal keep the game alive, we don't sell, we share for free just for the enjoyment of all and each one of us.
And, as everybody is aware, crap guys sell our free MODs on eBay and we cannot do anything against it.
I don't know if they have the right to deny or not. Anyway, I regret they do it!

Try this Ricardo: [www.youtube.com]

Thanks mate, I've tried all without success, including this one. I've sent a message to the author again and see what he will say.