To create new ssh keys on the server:

ssh-keygen -f /etc/ssh/ssh_host_rsa_key -N '' -t rsa
ssh-keygen -f /etc/ssh/ssh_host_ecdsa_key -N '' -t ecdsa -b 521

To check the fingerprint:

ssh-keygen -lf ssh_host_ecdsa_key

On the client side:

@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@    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 ECDSA key sent by the remote host is
SHA256:kY/TymCiskD0nhhyWaovohYvfCyZ7ymrEsmujeawaww.
Please contact your system administrator.
Add correct host key in /Users/monkey/.ssh/known_hosts to get rid of this message.
Offending ECDSA key in /Users/monkey/.ssh/known_hosts:236
ECDSA host key for [76.9.57.82]:2222 has changed and you have requested strict checking.
Host key verification failed.

To see the key on line 236:

awk 'NR==236' know_hosts

To remove the key:

ssh-keygen -R "[76.9.57.82]:2222"

Try to ssh again and veriy the key matches the one on the server.