[chirp_users] Version of Baofeng UV-5R not supported by CHIRP?

I have had success using both CHIRP and Baofeng software in downloading and uploading from a Baofeng UV-5R, Version BFB 251 120702 VER-05 which belongs to a mate. However, my own model UV-5R, Version BFB 291 120828N B5R0001 does not respond. Any suggestions? Regards,

Mike