No time conversion settings in App Settings 

Time conversion is now set up on a Project level. Go to Project settings. See Time Conversion settings in Admin Guide.

Right section (Issue Glance) doesn’t work / Section alignment settings are gone

From version 2.0.0 onward, Epic Timesheets doesn’t support Issue Glance panel view the same way it did before. Now all the information is displayed below your issue in the app’s own section.

Time Tracking section is disabled

Make sure that the Time Tracking section is enabled and the users are able to specify the estimated time and log the spent time.
Read more: Configure time tracking (Atlassian)

Custom Issue Types

Ensure that Epics are real Epics (not just custom issue type named Epic) provided by Jira Software.
Read more: Learn how to use Epics in Jira Software (Atlassian)