Looking at this link
https://www.cygwin.com/ml/cygwin/2014-03/msg00315.html
somebody's suggestion from the above link, seems to be a great checklist, exhaustive, no shortcuts and quick, and IIRC it worked for me.
Remove all files related to ssh from /etc.
Remove /var/empty.
Remove the ssh logs from /var/log.
Remove the sshd and cyg_server accounts from your SAM. Drop both from /etc/passwd.
Remove the sshd service. Start over.
Note- Where it says "start over", that might be american talk for restart, in this case, windows. Where it says to remove a service, you may need or want to stop the service before removing it. It may be that you don't need a restart, though you may. (so you could just only restart if it still didn't work). And where it says "your SAM" that means where it stores windows users - they're shown in 'computer management' - cygwin ssh adds users there, I see cyg_server and sshd users there, you can delete them from gui or command line. And re stopping and deleting a service, there are many commands that can. cygrunsrv, sc, net, and of those, i've not seen an advantage with cygrunsrv. and this jay guy thinks sc is more reliable at stopping or deleting them, that may be so. Other answers have you covered re commands to stop and remove a service.