@jcaron I update firmware of modem same as existing one then problem solved. now can communicate.

@ahmadelmasri Thanks so much! I can log in again!

@robert-hh I changed P8 to P9 and it works great! Thank you so much!

@melkoutch hope you still read this as this thread is quite old. I stumbled upon it having the exact same problem (LoPy4 <-> Feather M0 in raw LoRa). Adjusting the spreading factor doesn't seem to solve it for me. Would you be able to post the code fragment that you used to successfully connect the two? Thanks a lot!