Thanks Indigo, I think that has sorted the Advanced File Manager issue ( I just noticed the new File Manager button at the top of dashboard too. Nice stuff!
Now I just have the Postfix rebuild error as below. I've run email tests eg: DKIM, SPF and everything passes just can't get Postfix to rebuild without the error. I've looked in /var/log/maillog (now that file manager working) but TBH am not sure what I'm looking for in there.
Postfix error:Configuring...
Something wrong in Postfix, check log files please...