Why can raspberry pi access via ssh fall off?

Question

Raspberry Pi

Comrade sets up the device, tests it, works, starts up standard pi: raspberry via ssh.
throws me off that everything seems to be ready, it works. time difference with him 12 hours..
I'm poking - hell, Access denied. He does it with me, we test both me and him, it works. the next day the same garbage, does not let.
Who faced? Where to dig?