Putty is closing automatically

I have activated ssh on my NextCloud-Installation and then I wanted to login over Putty from my windows pc. At my first login, I have to change the password. After changing it and logging in again, then putty always shut down automatically.

Why? What can I do?

SSH is a service which is provided by the OS and has nothing to do with Nextcloud itself, therefore you will find guidance by searching for related information to the OS you’re using.