If you’re going to make an SSH connection to a common IP address like 192.168.1.1, you’ll get an error when you try to connect to a new device when you already connected to something else previously. It will look something like this.

@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@    WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED!     @
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!
Someone could be eavesdropping on you right now (man-in-the-middle attack)!
It is also possible that a host key has just been changed.
The fingerprint for the RSA key sent by the remote host is
SHA256:xxxx.
Please contact your system administrator.
Add correct host key in /Users/ryan/.ssh/known_hosts to get rid of this message.
Offending ECDSA key in /Users/ryan/.ssh/known_hosts:57
RSA host key for 192.168.1.1 has changed and you have requested strict checking.
Host key verification failed.

The solution is to disabled strict host key checking for that SSH session, but this is something you want to be careful about.

ssh -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null ubnt@192.168.1.1