Unison over SSH, connection with server lost although SSH works

I have just rebuilt my file server after it suffered disk corruption. When I tried to re-sync data using Unison, I got the error message > Lost connection with the server I retried from the command line and got: ~$ unison someprofile -ui text Contacting server... Unison failed: Fatal error: Error in creating unison directory /home/user/.unison: File exists [mkdir(/home/user/.unison)] Fatal error: Lost connection with the server I can open an SSH connection to the server. Both client and server run the same Unison version. What’s up here?