IN the past I’ve been able to reply to emails from Jira and have the contents of my email be automatically applied as a comment to the ticket. That doesn’t seem to work with New Jira installation. Can that be made to work?
What you require is easy to setup, you need to have an mail handler setup, details are here
You will need to contact your Jira admin for this.
It sounds like your new installation does not have mail handlers set up correctly to process incoming mail.
See https://confluence.atlassian.com/adminjiraserver071/creating-issues-and-comments-from-email-802592933.html as a starter (adjust for your Jira version, although it's not really changed between 7.0 and 7.11)