How to find out why SSH either asks for a password or not?

Question

linux

SLES12sp2 - Two virtual machines (copies) on two physical. computers.
You need a passwordless login from one to another via SSH (for RAC) and vice versa.
Tortured today these two machines under two users:
From one to the other works:
[email protected]> ssh-keygen
file path and passphrase answer Enter
ssh-copy-id node2
password 1
ssh node2 date
Gives the date without a password!
And on the other one it doesn't work:
[email protected]> ssh-keygen
file path and passphrase answer Enter
ssh-copy-id node1
password 1
ssh node1 date
asks for a password before issuing the date...
I deleted the ssh folders 10 times and tried it with passphrase (with an ssh agent), rebooted the computers and the machine's Wirth.
What could be the difference?
Now I tried it on other machines, under another user THE SAME THING to do and it turned out:

But I would like to understand how to diagnose why half a day was gone today and evening.
Of course, tomorrow, at work (on faulty machines), I'll try to re-create users, maybe they're the problem.)

Answer 1

Recreated users. Everything worked.