I recently upgraded Fisheye and crucible.
Priori t ot he upgrade I was able to log code review time in the code review and this passed back to JIRA. This is now disabled.
has the feature been dropped, if not how to enable it again
this feature wasn't removed from Crucible and should still be available. Which JIRA and Crucible versions are you using?
Logging time to JIRA issue might be disabled if you don't have time tracking enabled in JIRA, the user doesn't have the permission to track time, or the issue is in a state that doesn't allow time to be tracked. Internally (as of Crucible 3.5), we use the JIRA REST api to check whether work can be logged against the issue (using a call to /rest/api/latest/issue/ISSUE-1?expand=operations, and checking if the result contains an "operations-work" operation)