DKIM Not working on some of my servers

On the servers that it doesnt function correctly i get an error when disabling in email authentication saying: -

DKIM not disabled ([A warning occurred while processing this directive.]
.).


and when I enable it says: -

DKIM not enabled ([A warning occurred while processing this directive.]
.).


On these servers it doesn't sign my emails as it should, nor does it pass any dkim checks on other websites.

Hope you can help

thanks
robin