Gitlab jenkins integration "Host key verification failed"

am following
using gitlab ce (the docs above are for ee - is that going to be a problem?) 8.6.8 and Jenkins 2.1 on Linux.
I have created user in gitlab (jenkins), I can clone with this user. Copied private token and added itto Jenkins gitlab configuration.
But when I create the Jenkins project (maven project) and add Repository URL (which is git@Mint-Gitlab:norricorp/groovyTest.git), I get
Failed to connect to repository : Command “git -c core.askpass=true ls-remote -h git@Mint-Gitlab:norricorp/groovyTest.git HEAD” returned status code 128:
stderr: Host key verification failed.
fatal: Could not read from remote repository.

Please make sure you have the correct access rights
and the repository exists.

As I mentioned, I can log on as jenkins and do a git clone and that is successful.
Does anyone have any ideas on this?

Not sure what worked here but I did the following.
Rebooted system (I was going to bed anyway)
upgraded gitlab plugin in Jenkins
which caused a restart of Jenkins