Yes, same code and same SS pin (10)...in fact I clone the software with ICSP from nano to mini...but probably I find out the problem...Using DIGITAL OSCILLOSCOPE - Tektronix MSO4104 and digital probes, I saw that the SPI messages are identical for both nano and mini (I can see them directly in hex words),so my conclusion is that the issuue probably is in wiring. To check out I'm right I will do a more "clear" wiring setup and I will test signal with oscilloscope directly "after" wires before shift register chip
I will let you know
thank you