Why does Permission denied (publickey) fail on subsequent SSH connections?

Question

SSH

When creating a new instance and a pair of keys, the ssh connection proceeds normally. I also connect via FileZilla.
At the following connections, the message falls out. Permission denied (publickey).
At the same time, through FileZilla, everything works as before.
What's going on with key.pem and how to fix it?

Answer 1

write -vvv on your ssh connection and see detailed logs